Between physics and metaphysics: Mulla Sadra on nature and motion.

Mulla Sadra's concept of nature and substantial motion treats many aspects of traditional philosophy and cosmology in a new light. By allowing change in the category of substance (jawhar), Sadra goes beyond the Aristotelian framework followed by the Peripatetics and Suhrawardi, turning substance into a 'structure of events' and motion into a 'process of change'. Sadra's reworking of classical cosmology through his elaborate ontology and natural philosophy leads to a new vocabulary of 'relations' and fluid structures as opposed to 'things' and solidified entities. In his attempt to make change an intrinsic quality of the substantial transformation of things, Sadra posits nature (tabi'ah) as the principle of both change and permanence, thus granting it relative autonomy as a self-subsisting reality. What underlies Sadra's considerations of change and nature, however, is his concept of being (al-wujud) and its modalities. Change as a mode of being and the de-solidification of the physical world goes beyond locomotive and positional movement, and underscores the dynamism of the world-picture envisaged by Sadra's gradational ontology.

Keywords: Sadra; nature; change; substance; ontology; being; actuality; potentiality; matter; permanence; form; motion/movement.

Mulla Sadra's concept of substantial motion (al-harakat al-jawhariyyah) represents a major departure from the Peripatetic concept of change, and lends itself to a set of new possibilities in traditional Islamic philosophy and cosmology. By defining all change as substantial-existential alterity in the nature of things, Sadra moves away from change as a doctrine of external relations, as Greek and Islamic atomism had proposed, to a process of existential transformation whereby things become ontologically 'more' or 'less' when undergoing change. In his considerations of quantitative and qualitative change, Sadra takes a thoroughly ontological approach and places his world-picture within the larger context of his gradational ontology. Substantial motion and the dynamic view of the universe that it espouses can thus be seen as a logical extension of the primacy (asalah) and gradation of being (tashkik al-wujud)--two key terms of Sadrean ontology. Sadra relegates all reality, physical or otherwise, to the infinitely variegated and all-encompassing reality of being, and this enables him to see all change in terms of being and its modalities (anha' al-wujud). Although Sadra accepts a good part of the Aristotelian view of motion and its types, it is this ontological framework that distinguishes his highly original theory of substantial motion from the traditional Peripatetic discussions of motion.

In what follows, I shall give a detailed analysis of substantial motion and the ways in which Sadra incorporates and reformulates the traditional notions of qualitative and quantitative change in his natural philosophy. It should be emphasized at the outset that Sadra's views on nature and motion are not an isolated set of philosophical reflections but are rather closely related to his ontology and cosmology on the one hand, and psychology and epistemology, on the other. This is borne out by the fact that many of Sadra's novel contributions to Islamic philosophy are predicated upon substantial motion, among which we may mention his celebrated doctrine that the soul is "bodily in its origination, spiritual in its subsistence" (jismaniyyat al-huduth ruhaniyyat al-baqa') and the unification of the intellect and the intelligible (ittihad al-caqil wabl-macqul). In this essay, I shall limit my discussion to Sadra's attempt to move away from a framework of external relations and positional motion to a framework of existential transformation whereby the cosmos is projected as marching towards a universal telos.

The Aristotelian Framework: Motion as the Actualization of Potentiality

Following the scheme of Aristotelian physics, Sadra begins his discussion of motion by explaining the meaning of potentiality. The word potentiality (al-quwwah)(1) is defined in several ways. The most common meaning is the ability to execute certain actions. In this sense, al-quwwah as potency is synonymous with power (al-qudrah), which renders the motion or action of physical bodies possible. Ibn Sina gives a similar definition when he says that "potentiality is the principle of changing into something else". (2) All beings that undergo quantitative or positional change use this potential power. Such corporeal bodies, however, need an active agent to actualize their dormant potentiality. For Sadra, this proves that a thing cannot be the source of change by itself, and there must be an outside factor to induce it to change. If the source of a quality or 'meaning' (ma'na) in an entity were to be the thing itself, this would amount to an unchanging nature in that thing. The real nature of possible beings, however, displays a different structure. With Aristotle (3) and Ibn Sina (4), Sadra takes this to mean that "a thing cannot have its principle of change in itself" and that "for every moving body, there is a mover outside itself". (5)

The relationship between a mover and a moving object presents a causal hierarchy in that the mover that sets other things in motion is not only actual but also enjoys a higher ontological status. (6) In Sadra's terms, whatever has priority and more intensity in existential realization (ashaddu tahassulan) is likely to be more a cause and less an effect. In this general sense, it is only God who is rightly called the 'cause' of everything. By the same token, materia prima (al-maddat al-ula/hayula) has the least potentiality of being a cause because it is weakest in existential constitution with a strong propensity towards non-existence. (7)

After stating that motion and rest (al-sukun) resemble potentiality and actuality and belong to the potentiality-actuality framework, Sadra defines them as accidents of being-qua-being because being-qua-being is not subject to motion and rest unless it becomes the subject of natural or mathematical order. (8) At this point, an existing body capable of motion must bear some potentialities and some actualities. A purely potential being cannot have any concrete existence as in the case of the prime matter (al-hayula). The state of a purely actual being, on the other hand, cannot apply to anything other than God who has no potentiality to be actualized. A being of such a nature should be a "simple being that contains in itself everything". As the Peripatetics before Sadra had argued, prime matter is 'infinite' because it is indefinite and ready to take on any form when realized by an actual form. As for contingent beings capable of motion, which refers to the world of corporeal bodies, they have the potentiality of gradual (tadrijan) transition from potentiality to actuality.

The temporal term 'gradual' in the definition of motion, however, had caused some problems for Muslim philosophers because the definition of movement as gradual transition from potentiality to actuality implies that this process occurs in time. Although this statement is acceptable in the ordinary use of language, definition of time as the measure of motion leads to petitio principi and regression. This led some philosophers to propose a new definition of motion that contains no terms of time. Relying on Ibn Sina, Suhrawardi and al-Razi, Sadra rebuts this objection by saying that the meaning of such terms as 'sudden' and 'gradual' is obvious with the help of the five senses, i.e., through physical analysis. (9) There are many clear and obvious things, says Sadra, whose inner nature we can never fully know. (10) Nevertheless, this explanation did not satisfy the theologians (11,) and, following Aristotle (12), they defined motion as the realization of what is possible (mumkin al-husul). Since this definition indicates a move from potentiality to actuality and since actuality always implies perfection as opposed to potentiality, motion also signifies an act of perfection. Hence the conventional idea that motion is perfection for the moving body. But this perfection is necessarily different from other types of perfection because it has no real existence other than 'passing to another place'. Understood as such, a moving body possesses two special characteristics. The first is inclination (tawajjuh) towards a particular point or aim (matlub), which Sadra associates with the inner nature of things. The second is that there should remain some potentialities in things that move even after they exhaust their potentiality to move towards a particular position. This implies that motion and rest resemble potentiality and actuality only in a limited sense. (13)

The above definition of motion leads to the commonly held idea that motion is the first perfection for a potential being in so far as it is potential. This definition, says Sadra, goes back to Aristotle. Plato provides a similar explanation: It is coming out of the state of sameness, i.e., a thing's being different from its previous state. Pythagoras proposes a close definition: It consists of alterity. After mentioning these definitions and their partial criticism by Ibn Sina, Sadra states that these different definitions refer to one and the same meaning, which is the essential change of state of affairs in the moving body. Sadra then criticizes Ibn Sina's objection to Pythagoras that motion is not change itself but rather 'that by which change takes place'. Sadra rejects Ibn Sina's view by saying that motion is not a 'thing' or agent by which things change. To define motion, as the Mutazilites claimed (14), as an agent through which things move is to posit it as an accidental property of things--the very view against which Sadra proposes his substantial motion. Instead, he insists on the definition of motion as change itself. As we shall see below, Sadra pays a particular attention to this point because it is closely related to the renewal of substantial natures (tajaddud al-akwan al-jawhariyyah) on the one hand, and continuously changing nature of things (tahawwul al-tabi'at al-sariyah), on the other. (15)

Two Meanings of Motion

In the Shifa', Ibn Sina gives two different meaning of motion: the first is the 'passage' (qatc)16 view of motion according to which the moving body is taken as a present whole during movement. When the mind considers the moving body with the points that it traverses, it pictures these discrete points and time-instants as a present whole. But since this frozen picture corresponds to a body extended in space and time as a continuous whole rather than to an actual change, this kind of motion exists only in the mind. The second kind is called 'medial motion' (tawassut) because, according to this view, the moving body is always found somewhere between the beginning and end of the distance traversed. This view, however, refers to a state of continuation, viz. the body's being at a point at every time instant. As such, it does not allow change in the existential constitution of moving bodies but simply states a transposition from one place to another. For Ibn Sina and Sadra, it is this kind of motion that exists objectively in the external world.

Having no quarrel with the medial view of motion, Sadra sets out to prove the objective existence of motion as passage. He first draws attention to a self-contradiction in Ibn Sina's rejection of it. Ibn Sina accepts time as something continuous in the external world because it can be divided into years, months, days, and hours. It is the very definition of time that corresponds to motion as passage. Upon this premise, Ibn Sina regards passage motion as the locus and cause of time. But if passage motion does not exist objectively, how can it be the measure of time? In other words, how can something non-existent be the locus of something existent? (17)

Ibn Sina's denial of the passage view of motion results from his understanding of motion as an accidental property of physical bodies. A physical body is a stable substance that exists in every instant of time insofar as it exists. But motion has no existence in time-instants (an). If motion were one of the modalities of things, it would always have to be together with them. Motion exists in things only continuously (istimraran) which, in turn, refers to the second meaning. To this, Sadra replies by saying that the locus of motion is not the thing as a stable substance but as the locus and place upon which an action is exercised. In order for a thing to receive motion and change, it should undergo some kind of change in its essential structure (darb min tabaddul al-ahwal al-haythiyyah). This is based on the idea that 'the cause of that which changes also changes' (cillat al-mutaghayyir mutaghayyir), and, likewise, 'the cause of that which is stable is stable' ('illat al-thabit thabit). (18)

The main reason for the denial of the passage view of motion is related to the peculiar characteristic of this type of motion, which Sadra describes as having 'weak existence'. As the following quotation shows, 'weak existence' refers to existential dependence, namely to the fact that things of this sort are not self-subsistent and always caused by an agent:

   Motion, time and the like belong to the category of
   things that have weak existence (da'ifat al-wujud).
   Accordingly, their existence resembles their non-existence,
   their actuality is similar to their potentiality,
   and their origination (huduthiha) is nothing but their
   corruption (zawaliha). Each of these (qualities or
   attributes) requires the non-existence of the other; in
   fact, their existence is their non-existence. Therefore,
   motion is the very destruction of a thing itself after it
   (is established in the physical world) and its origination
   before it (is actualized in the external world). And this
   mode (of being) is comparable to the absolute being in
   the sense that all relational beings (al-idafat) have some
   sort of existence. Likewise the existence of motion
   displays ambiguity (shukuk) and similitude (shabah) (of
   being close to both being and non-being). (19)

Within the actuality-potentiality framework, there are, Sadra states, two poles of existence. The first is the First Reality or the Absolute Being, and the second the first hyle. The former, which contains no potentiality in and of itself, is pure goodness par excellence, and the latter, which is pure potentiality with no actual existence, is 'evil' containing in itself no goodness save accidentally. Nevertheless, since the hyle is the potentiality of all beings, i.e., the indefinite substratum ready to take on any form in actuality, it has some share of goodness as opposed to non-existence ('adam), which is pure evil. What Sadra calls the "First Reality" (al-haqq al-awwal) terminates the chain of active agents that bring potential beings into a state of actuality, and thus functions as a cosmic principle in the 'great chain of being'. The ontological discrepancy between potentiality and actuality points to a hierarchy of beings in that things that are in actuality enjoy higher ontological status. At this juncture, Sadra insists that a simple body is always composed of matter and form because it has the potentiality of motion on the one hand, and contains 'the material form' (al-surat al-jismaniyyah) or a single continuous substance (al-ittisal al-jawhari), which is something actual, on the other. This aspect of physical substances proves one of the cardinal principles of Sadrean ontology and natural philosophy, i.e., that 'a simple reality is ... all things' (basit al-haqiqah ... jami' al-ashya'). (20)

The Mover and the Moving Body

We may remember that Aristotle had proposed the concept of the Prime Mover to terminate the infinite regression of causal chain. Put simply, if everything is moved by something else, this must end in an agent that itself does not move. An important consequence of this idea is the stark distinction between the mover and the moving body--a complementary duality that was extended in posterity to positional motion. Considered from the perspective of vertical causality, every moving body needs a mover, and Sadra, following the Peripetatics, reformulates this relationship in terms of actuality and potentiality. Since the process of motion requires the two poles of actuality and potentiality, actuality refers to the mover (al-muharrik), and potentiality to the moving body (al-mutaharrik). In other words, the mover as the actual being provides the cause of motion, and the moving body as the potential being stands at the receiving end of the process of motion.

This polarity shows that a single body cannot be both the active and passive agent of motion. In other words, we have to assume the existence of a prime mover to which all motion can ultimately be traced back. Sadra's argument runs as follows: The moving body, in so far as it is a potential being, has to be a passive agent, i.e., the receiver of the act of motion whereas the mover has to be an active agent, in so far as it is an actual being. These two qualities or 'aspects' (jihat) cannot be found in the same thing simultaneously due to their exclusive nature. In other words, a physical entity cannot be both the source and locus of motion at the same time. At this point, all motion should go back to an active agent which is

   different from motion as well as from the locus of
   motion, moving by itself, renewing itself by itself, and
   necessarily the source of all motion. And this (agent)
   has its own agent (i.e., principle) of motion in the sense
   of being the source of its own continuous renewal. By
   this, I do not mean the 'instaurer' (ja'il) of its motion
   because instauration cannot exist between a thing and
   itself. This is so because the direct agent of motion has
   to be something in motion. Otherwise this would
   necessitate the difference of the cause (al-'illah) from its
   effect (ma'luliha). Thus, if this (chain of causation) does
   not end in an ontological agent (amr wujudi) that
   renews itself by itself, this would lead to regression or
   circularity.' (21)

Sadra goes on to adduce proofs for the necessity of a prime mover as an external agent to set things in motion. He rejects and responds to some objections as follows. 1) If a thing were to move by itself, it would never reach rest because whatever endures by itself does so by its intrinsic qualities. Once these qualities or properties are disjoined from a thing, it no longer exists. 2) If a thing were to move by itself, parts of motion i.e. the subject of motion as a whole would be in rest, which means that the thing would not move. 3) If the principle of motion were to be in the moving body itself, it would have no 'fitting' or natural place to which it could incline. According to the conventional definition of motion, however, if there were to be no natural place for a thing to which it could incline, it could not move. 4) If self-motion were to be a real property of a moving body, it would be a universal quality of 'thing-ness' (shaybiyyah) shared by all corporeal things. But this is not the case in natural bodies. In reality, says Sadra, motion is a particular quality provided by an outside mover. 5) Another proof for the fact that a physical body cannot have the principle of motion in itself is that this would mean that both potentiality and actuality can be found at the same locus simultaneously. If this were the case, actuality would not be succeeded by potentiality. Because according to the definition given above, motion is the first perfection for what is potential. If a thing were able to move by itself, it would be actual in all respects without leaving any room for potentiality, which is obviously inconceivable for contingent beings. 6) The relation of the moving body to motion is established through contingency (bi'l-imkan), and its relation to motion as an active agent is necessary (bi'l-wujub). If the moving body itself were to be the producer of motion, this relation would be necessary. But since contingency and necessity cannot coincide, the moving body has to be different from the principle or source of motion. (22)

How Things are Set in Motion

There are two possible ways for a mover to set things in motion: It moves things either 1) directly and by itself or 21 indirectly and by means of something else. A carpenter with his adz is an example for the second type of motion. The immediate act of the mover gives the concept of motion as an accidental property. The act of the mover by means of something else yields the notion of the moving body itself. The mover sets an object in motion without being in need of an intermediary agent like the attraction of the lover by the beloved or the motion of the one who has zeal and desire to learn by the learned one. The first mover, which itself does not move, either grants the moving body the immediate cause by which it moves, or attracts it to itself as its final goal. Everything in the physical world brings about a certain effect not by accident or coincidence but through an extraneous power added to it from outside. And this 'added quality' is either the nature it has or the voluntary power it possesses. In both cases, this power should be related to the thing itself viz., it cannot be totally 'relationless' in respect to it. If this were a kind of motion brought about by the abstract or 'detached' agent (al-mufariq) in a universal manner, this would amount to something other than what is meant by motion in the usual sense of the word. Therefore, the Prime Mover needs and, in fact, employs in things an 'agent' by means of which it sets them in motion. This agent in all contingent beings is 'nature' (tabi'ah). (23)

The next problem Sadra addresses is how the Prime Mover, which itself does not move, is related to contingent beings and material bodies. We may summarize Sadra's argument as follows: A thing's being capable of receiving the effect of motion from the 'detached' agent (al-mufariq) can be attributed to three reasons: the thing itself, some special quality in that thing, or a quality in the detached agent. The first is impossible because, as shown previously, this would lead us to accepting motion-by-itself as a universal and intrinsic quality of thing-ness. Sadra briefly states that the second option i.e., motion through a property or ability in things is the right view. The third option has some points to consider. The actualization of motion through an aspect of the detached agent takes place when the detached agent originates an effect in the thing it sets in motion. This, in turn, may happen either through the will of the detached agent by manipulating something in the thing or through effecting it haphazardly according to its wish.

The last option is not tenable because it terminates the idea of order in nature. Chances or accidental coincidences (al-ittifaqiyyat), says Sadra, are not constant and continuous in nature:

   Chances, as you will learn, are neither constant nor
   dominant (in nature) whereas order in nature is both
   dominant and continuous. There is nothing in nature
   that happens by chance or haphazardly. As you will
   learn, everything in nature is directed towards a
   universal purpose (aghrad kulliyah). Thus, the effect of
   motion cannot be brought about by chance. What
   remains, therefore, (as a valid option) is a particular
   quality in the physical bodies (that move). This
   essential quality (al-khassiyyah) is the source of motion,
   and this is nothing but potency (al-quwwah) and nature,
   by virtue of which things yearn, through motion, for
   their second perfection. (24)

Thus, we are left with the option that this effect occurs by means of an essential quality in physical bodies, which causes them to move. This Sadra calls 'potency' and 'nature'. (25)

After positing 'nature' as the immediate cause of all motion (26), Sadra opens a long parenthesis and delves into a discussion of how actuality precedes potentiality. This long discussion is meant to show that the very idea of contingency requires existential transformation and that the continuous renewal of contingent beings is an essential quality that exists in concreto whenever possible beings are brought into actuality out of potentiality. Sadra's arguments also reveal some interesting aspects of his theory of matter. Every created being is preceded by being (wujud) and 'some matter' (maddah) that bears it. This is a quality inherent in all contingent beings. Otherwise they would belong to the category of either necessary or impossible being. Matter with which contingent beings are united acts as one of the immediate principles or causes of bringing contingent beings out of non-existence and pure potentiality. It is to be remembered that matter and form, just like potentiality and actuality, are not 'things' but principles of existence. In this sense, the subject of contingency (mawdu' al-imkan) has to be an originated entity (mubdi'an), otherwise it would be preceded by another contingency ad infinitum. Every possibility vanishes when it becomes something actual in the external world. This means that every contingency is preceded by another one until the chain of causation comes to an end in the Principle which has no contingency, i.e., potentiality.

Sadra warns against the idea that potentiality is prior to actuality in an absolute sense. In fact, it is a common tendency to put potentiality before actuality like a seed's relation to a tree or like Nazzam's celebrated theory of 'latency' (kumun and buruz). (27) Some have said that the universe was in disorder and God bestowed upon it the best of all orders. In the same manner, matter has been regarded prior to form, and genus to differentia. According to another group of people whom Ibn Sina mentions in the Shifa', the hyle had an 'existence' before its form, and the active agent gave it the dress of the form. Some have held the view that all things in the universe were moving by their natural motion without any order. God arranged their motion and brought them out of disorder.

Sadra's overall reply to these claims is that in some cases, as in the relationship between sperm and man, potentiality precedes actuality in time. But, in the final analysis, potentiality cannot subsist by itself and needs a substratum to sustain it.

   We say that, as far as particular entities in the world of
   corruption are concerned, the relation between
   (potentiality and actuality) is like the sperm and the
   human being. Here, the potentiality specific (to the
   sperm) has priority over actuality in time. But
   potentiality, in the final analysis, is preceded by
   actuality for a number of reasons. Potentiality (i.e., the
   potential being) cannot subsist by itself and needs a
   substance to sustain it. And this substance has to be
   something actual (bi'l-fi'l) because whatever is not
   actual cannot exercise (any power) on something else.
   By the same token, whatever is not existent in an
   absolute way cannot accept any (exercise of power).
   Furthermore, there are certain actual beings in
   existence that have never been and are by no means
   potential in essence such as the Sublime First
   (Principle) and the Active Intellects (al-'uqul al-fa''alah).
   Then, potentiality needs the act (fi'l) (of realization) to
   bring it into actualization whereas this is not the case
   with what is actual. Potentiality needs another agent
   (mukhrij) to bring it (out of non-existence), and this
   chain undoubtedly comes to an end in an actual being
   (mawjud bi'l-fi'l) which is not created (by something
   else) as we have explained in the chapter on the
   termination of causes. (28)

After these considerations, Sadra introduces an axiological element into the discussion, which, in turn, confirms the ontological discrepancy that Sadra establishes between potentiality and actuality on the one hand, and existence and non-existence, on the other.

   Goodness (al-khayr) in things comes from the fact that
   they are actual whereas evil (al-sharr) stems from what
   is potential. A thing cannot be evil in every respect
   otherwise it would be non-existent. And no being, in so
   far as it is something existent, is evil. It becomes evil as
   a privation of perfection such as ignorance, or it
   necessitates its own non-existence in other things such
   as injustice (al-zulm).

   Since potentiality has some sort of actualization in the
   external world, its essence subsists by existence. And
   existence, as you have seen, is prior to essence in an

   absolute way. Therefore, potentiality as potentiality has
   external realization only in the mind. Thus, it is
   concluded that whatever is actual is prior to the
   potential in terms of causation (bi'l-cilliyyah), nature
   (bi'l- tab'), perfection (bi'l-sharaf), time, and actual
   reality (bi'l-haqiqah). (29)

Nature as the Immediate Cause of Motion

As we have stated previously, motion is the act of moving itself (mutaharrikiyyat al-shay') for it refers to the continuous renewal and lapse of the moving body in a particular time-space coordinate. This point is of extreme importance for Sadra's purposes here for he tries to establish motion as an essential property of corporeal bodies, and this is a major step towards substantial motion (al-harakat al-jawhariyyah) as opposed to positional or locomotive motion. In this sense, the immediate cause of motion should be something whose essence is not stable. Otherwise 'a stable or enduring entity will contain in itself the passing phases of motion as a present fact, and this togetherness of all passing phases would amount to stability, not motion.' (30) This leads Sadra to the following conclusion: The immediate cause of every motion should be something whose quiddity (mahiyyah) is stable but whose being (wujud) is ever-changing.

   The immediate cause of motion has to be something
   with a stable essence and continuously changing being
   (thabitat al-mahiyyah mutajaddid al-wujud). As you will
   see, the immediate cause of all kinds of motion is no
   other than nature. This nature is the substance by
   which things subsist and become actualized as a species
   (i.e., as a particular entity) (31). This refers to the first
   perfection of natural things in so far as they are actual
   beings (in the external world). Therefore it is
   concluded and established from this (consideration)
   that every physical being is a continuously changing
   entity with a flowing identity (sayyal al-huwiyyah) despite
   the fact that its quiddity is impervious to change. (32)

The statement that the subject of motion should be something with a stable essence is true only when we mean by 'stable' (thabit) the quiddity (mahiyyah), viz., the mental image of things. Or, we understand from 'stable' the subject of motion, which is not a concomitant (lazim) for the actual existence of the thing in question. To emphasize this point, Sadra introduces two kinds of motion. The first is the kind of motion which every material substance possesses as a concomitant of its existential constitution. In other words, this kind of motion exists as an essential property of corporeal things, and confirms substantial motion as a principle of 'substantiation'. The second kind of motion is that which takes place as an 'accident' as in the case of transposition (naql), transformation (taghayyur) or growth. Sadra calls the latter 'motion in motion' (harakah fi harakah). (33)

In light of this view, we can say that every moving body possesses and preserves a 'nature' that acts as its immediate cause of motion. This nature, however, is not something superadded to things from outside, like an accident, but conjoined with their substances. Thus nature is not only the immediate cause of natural motion (al-harakah al-tabi'iyyah) but also that of forced or constrained (al-harakah al-qasriyyah) motion. In the latter case, any mover that moves something else uses 'nature' as agent of motion. In other words, it is this nature that renders possible both primary, i.e., substantial, and secondary, i.e., accidental movement. This is where Sadra takes his departure from traditional accounts of motion.

   And we are certain about the following conclusion on
   the basis of heart-knowledge (al-wijdan) rather than
   discursive proof (al-burhan): the cause that makes a
   thing yield and induces it to move from one place to
   another or from one state (of being) to another cannot
   but be an actual power inherent in that thing. This is
   called nature. Thus, the immediate cause of material
   [i.e., physical] motion (al-harakat al-jismiyyah) is the
   substantial power that subsists in things, and all the
   accidents are subservient to the sustaining form (al-surah
   al-muqawwimah), which is nature ...

   The philosophers have shown conclusively that every
   (physical body) which accepts the act of yielding (al-mayl)
   from outside has to have a natural inclination
   (mayl tibaci) in itself. It is thus proved that the direct
   source of motion is something flowing with a
   continuously changing identity (mutajaddid al-huwiyyah).
   If this (substratum) were not to be something flowing
   and ever-changing, it would be impossible for these
   natural motions to emanate from it on the basis of the
   principle that the ever-changing cannot emanate from
   the stable. (34)

We may read this paragraph as an indirect response to Ibn Sina. Sadra's claim is that Ibn Sina has in fact accepted the principle that a stable being cannot be the cause of instability and permanent change at the same time. In other words, Ibn Sina is to be corrected on the principle that any change and transformation that we observe in things externally goes back to the constantly changing structure of their substance. Every direct or indirect motion is ultimately connected to and an outcome of nature that corporeal bodies possess.

Nature as the Principle of Change and Permanence

After criticizing the philosophers' idea of 'two consecutive phases' in motion, (35) Sadra discusses briefly the problem of how changing things (mutaghayyir) are related to an unchanging and permanent principle (thabit). If every changing body is preceded by another changing body, this leads either to an endless chain or to a change in the First Principle, which we have already ruled out as impossible. Sadra eliminates this objection by saying that the continuous renewal of material bodies is their essential attribute, not a quality added to them from outside. When a corporeal thing moves towards its 'existential realization', viz., actualizes its potentialities by going through various forms and states of being, such as emerging from potentiality to actuality or moving from one location to another, it possesses its immediate cause of motion/change in itself, and does not need an extra 'cause'. Even when an extraneous stimulator is required for a thing to move externally, this is made possible only by having recourse to the nature inherent in things.

The gist of the foregoing arguments is that every natural body carries the principles of change and permanence in itself simultaneously. Nature, for example, remains an enduring property in physical bodies while its very reality is change. By the same token, there are certain things whose actuality is their potentiality such as the hyle, or whose plurality is their unity such as the numbers, or whose unity is their plurality such as the material body with its components as a whole. (36) Thus, everything has a dual structure in its essential constitution. In this respect, nature and hyle appear to be the two basic points of connection between the changing and the unchanging.

Considered in its aspect of permanence, nature is directly connected to the permanent principle. When considered in regard to its aspect of change and renewal, however, it is connected to the renewal of material bodies and the origination of created beings. In a similar way, the hyle serves as the connection point between the potentiality and actuality of contingent beings. It is thus concluded that "these two substances (i.e., nature and hyle) are simply means of origination and corruption of material bodies, and through them a relation is established between the eternal (al-qadim) and the created (al-hadith)'. (37)

Category of Motion

The question of which categories (maqulat) are capable of receiving change and motion is of particular significance for Sadra because substantial motion is ultimately nothing but change in the category of motion itself. We may remember that Ibn Sina, following Aristotle, had accepted change in categories such as quality, quantity and position but denied it in the category of substance (jawhar). Since substance was regarded by al-Shaykh al-Ra'is and his students as a stable substratum to which all accidental qualities are traceable, accepting change in the substance of a thing would amount to the dissolution of that particular thing, and, as a result, there would remain no subject or substratum for motion and change. For Sadra, however, since a stable substratum is not needed to support the 'general existence' of a physical body, change in the category of substance does not lead to destruction of corporeal bodies. This is predicated upon the principle that the subject of motion is 'some subject' (mawdu' ma) rather than a 'particular subject' (mawdu'). In other words, what is needed through the process of substantial change is not a particular locus or substratum, which would be destroyed by qualitative or quantitative change, but some subject that remains constant. We may summarize Sadra's analysis as follows.

When we say that motion is 'within a category' (maqulah), four possibilities arise to consider: 1) the category is the subject of motion, 2) substance through a category is the subject of motion, 3) the category is a genus for motion, and finally 4) the substance itself is changing gradually from one species to another or from one class to another.

Sadra emphatically rejects the first three possibilities by repeating his fundamental identification of the act of motion with the moving body. He repudiates the claim of the earlier philosophers that if we admit change in one of the four categories, then we would have to accept an infinite number of species being actualized in one single entity. It is obvious, however, that the realization of an infinite number of species in a finite being is impossible. In this respect, Sadra invokes Ibn Sina in support of his argument by quoting from the Ta'liqat. What happens during the essential change of categories is not that at every successive moment, a new amount of quantity is added up to the thing which maintains its previous existence in terms of quantity. In reality, the infinite number of species exists only potentially due to the very definition of motion, i.e., that it is an intermediary stage between pure potentiality and pure actuality. During the process of motion, a physical body, which goes through various degrees of existence, "has a temporal particular quanta-entity which is continuous, gradual and in perfect proportion with the time instants of motion". (38)

Such a body has an infinite number of 'instantaneous individuals' (afrad aniyah) at every second. But these 'infinite instantaneous individuals' exist only potentially and do not point to a real actualization in the extra-mental world. Blackness, for instance, has an existence in actuality, which is of such a nature that the mind can abstract from it a series of new species at every instance. This particular existence of blackness is 'stronger' than 'instantaneous existences' (i.e. the possible species abstracted by the mind) in that as an actual existent, it represents (misdaqan) in itself many species. By the same token, an animal's existence is stronger than a plant's existence because, as a single unity, it contains and represents every shade of existence that the plant possesses. The same holds true for the intensification of blackness since it encapsulates whatever blackness exists in 'weak black entities'. Thus, motion or change does take place in categories, and Sadra accepts this as the only possible view. (39)

As for the view that the category of substance is a species for motion, it is not tenable because, as Sadra repeatedly states, "motion is not the changed and renewed thing but the change and renewal itself just like immobility is not the immobile thing but the immobility of a thing". In this regard, it should be emphasized that the establishment of motion for constantly renewing bodies is not like the occurrence of an accident to a 'self-subsisting subject' (al-mawdu' al-mutaqawwim bi-nafsihi). The idea of such a stable subject is rather one of the 'analytical [i.e., mental] accidents' (al-'awarid al-tahliliyyah) i.e. mentally abstracted and posited accidents that the mind constructs. This, in turn, underscores the intrinsic relation between existential motion and actually existing entities, and affirms that the 'separation' of substantial motion from corporeal things is nothing but an outcome of our mental analysis. The 'occurrence' ('urud) of motion to things is an event that takes place only at the level of conceptual analysis viz., when the mind analyzes an actually existing entity into its constituent parts. In a sense, this is comparable to the distinction between essence (mahiyyah) and existence (wujud) - a distinction that exists only in the mind. Thus Sabzawari states that the distinction is merely a matter of 'naming' (bi-hasab al-cunwan). (40) At best, the attribution of mental accidents to subject can be compared only to the attribution of differentia (fasl) to genus (jins).

Sadra sums up his discussion by saying that "the meaning of motion being in a category is that the subject (i.e., the substance) is bound to change gradually, and not suddenly, from one species to another or from one class to another." (41)

Problem of Quantitative Change

Even though the Peripatetics had affirmed, with Aristotle, that all categories, with the exception of substance, undergo change, explaining the precise nature of quantitative change has posed some difficulties. (42) Sadra even says that Suhrawardi and his followers had denied quantitative change. (43) The main difficulty seems to result from the assumption that increase and decrease in quantity necessitates the replacement of the original quantity as well as that which is quantified, i.e., the physical body that undergoes quantitative change. In contrast to the idea of quantitative change as rupture and replacement, Sadra sees change in quantity as a continuous and single process. His detailed discussion can be summed up as follows.

Since motion signifies the actualization of certain qualities and quantities that exist for physical bodies potentially, Sadra reverses the picture and says that to become black means not the increase of blackness in the subject but rather the increase of the subject in blackness. In other words, it is not the case that during quantitative increase or decrease, there exist two blacknesses, the original blackness and the newly emergent one. The mind conceives this process as the conjoining of two separate and discrete quantities of blackness. When conceived as such, it becomes impossible to explain quantitative change because such a process corresponds not to the gradual augmentation or diminution of something but rather to the juxtaposition of two independent quantities. In the order of existence, however, blackness has only "one single identity (huwiyyah shahksiyyah wahidah) evolving in perfection at every instant". (44)

When we say that blackness has only 'one single continuous identity' (huwiyyah wahidah ittisaliyyah) in the process of quantitative augmentation or diminution, we admit some 'degrees of intensification' (maratib al-ishtidad). In this case, says Sadra, three points should be made clear. First of all, there is an infinite number of species in one single entity only in potentia. In the order of existence, this fact is complemented by the principle that "one single continuum has only one single being" (al-muttasil al-wahid lahu wujud wahid).45 Secondly, although blackness has one single continuous identity in its perfection or imperfection, 'various species, essential properties and logical differentiae' occur to it in regard to its existential renewal. For Sadra, such a transformation in the substance of physical bodies is possible because it is being (al-wujud) that is fundamentally real and principial, quiddity being thereby subject to it. The reason why Sadra invokes the primacy of being here is that he considers the ever-expanding reality of being as the primary context of all substantial change. Thirdly, the frozen picture of an increasing entity presents to the mind some instant-points that have occurred actually and some instant-points that may occur potentially. As Sadra repeatedly states, however, it is the mental representation of the order of being that yields the idea of quantitative change as a succession of two discrete species or entities. In contradistinction to the Peripatetics, a corporeal body that undergoes quantitative change always maintains its identity as a single and unbroken unity. Thus, an entity of this nature is

   a new emergent every moment with a continuous body
   in respect of which if we say it is one, we would be right
   or if we say it is many,... enduring or changing, all
   these would be right. If we say that it persists
   identically from the very beginning of change to the
   end, we shall be speaking the truth; if we say every
   moment it is a new emergent (hadith kulla hin) this will
   be equally true. (46)

To further emphasize motion as a continuous process, Sadra turns to Ibn Sina one more time and takes him to task on the question of motion in the category of substance. We may remember that Ibn Sina had conceived motion in substance not as a single continuum but rather as the sudden destruction of original substance and its replacement by another one. Ibn Sina's criticism was based on the assumption that if substance were capable of intensification and diminution, the species that determines and particularizes it would either remain the same or change into another species. In either case, however, we would have to accept that there has been no change in the substance or that the original substance has been destroyed.

Against this criticism, Sadra provides the following answer, which sums up his doctrine of the gradual perfection of being in terms of plurality-in-unity and unity-in-process.

   If in the statement: 'either its species persists during
   intensification' by 'persistence of species' is meant its
   existence, then we choose that it does persist because
   existence as a gradually unfolding process has a unity,
   and its intensification means its progressive perfection.
   But if the question is whether the same specific
   essence, which could be abstracted (by the mind) from
   it, still continues to exist--then we choose to say that
   it does not remain any longer. But from this, it does
   not follow that an entirely new substance, i.e., existence
   has arisen; it only means that a new essential
   characteristic (or specific form) has been acquired by it
   (i.e., by existence...). That is to say, this substance
   either has been perfected or has retrogressed (the
   latter however does not actually happen) in the two
   modes of existence and hence its essential
   characteristics have been transmuted. This does not
   mean that an actual infinity of species has arisen (just
   as it did not mean in the case of black that an actual
   infinity of black colors had arisen); it only means that
   there is a single continuous individual existence
   characterized by a potential infinity of middle points in
   accordance with the supposed time-instants in the duration of its
   (moving) existence ... There is no difference between the qualitative
   intensification called 'change' and the quantitative intensification
   called 'growth' (on the one hand), and the substantive
   intensification called 'emergence (takawwun)' (on the other) in that
   each one of them is a gradual perfection, i.e., a motion towards the
   actuality of (a new) mode of existence. (47)

The gist of the foregoing argument is that being, as an unfolding single unity (al-wujud al-muttasil al-tadriji), travels through various essences, and assumes different forms and modalities. The gradual passing of a substance from one state of being to another means that it reaches a higher and more perfect mode of being at every successive point of movement. As we have stated before, however, this continuous process does not dissolve substances into different and discrete units.

Identity and Endurance of Physical Bodies

A particular problem arises here as to how to account for the endurance of substantial forms when corporeal bodies undergo qualitative and quantitative change. To establish a substratum that endures throughout the process of change, Sadra argues that 'some matter' (maddatun ma) particularized through a form, quality or quantity is enough for substantial change. In the course of the gradual perfection of a substance, a certain amount of matter (existence) remains as the persisting principle while taking on various forms, qualities, quantities, and positions. According to Sadra, the persistence of a certain amount of matter with its variegated modifications and particularizations is so subtle that the previous philosophers, including Ibn Sina, had acknowledged that the mind is incapable of perceiving it in its entirety. After stating this historical point, Sadra turns to the peculiar relationship between form and matter as an essential property of physical bodies. (48)

In Sadra's view, the riddle of quantitative change, which has led many philosophers, including Suhrawardi and Ibn Sina, to denying change in the category of substance, can be solved by having recourse to the following principle: what is required in the process of motion is not a definite quantity but 'some quantity' (miqdarun ma) by which things become particularized. Suhrawardi's problem had arisen out of the assumption that

   adding a certain amount of quantity to another (block of) quantity
   (i.e., the increase or decrease of a certain quantity) necessitates
   the destruction of the original quantity, and when a part of this
   quantity is taken away from the whole, this also necessitates the
   destruction (of that which is quantified). (49)

In this view, any quantitative change in terms of increase or decrease leads to the destruction of the original body/substance. Ibn Sina had faced a similar difficulty when explaining change in organic bodies. In fact, Ibn Sina "was not able to solve" the problem of identity in plants and animals because he had postulated that unlike man who has both soul and character, organic bodies, i.e., plants and animals, possess no enduring quality. (50)

In response to these difficulties, Sadra asserts that

   the subject of motion is a particular entity (al-jism
   al-mutashakhkhas), not a definite quantity (al-miqdar
   al-mutashakhkhas). And the particularization of a thing requires a
   definite quantity for the thing in its motion from one place to
   another as the physicians (al-atibba') have asserted with regard to
   personal character (al-mizaj al-shakhsi). The motion takes place in
   the particularizations and (various) stages of quantities. Therefore
   what is enduring from the beginning to the end of motion is
   different from what is changing. The disjunction (al-fasl) and
   conjunction (al-wasl) (of a definite quantity with matter) do not
   cancel each other out except in the case of conjoined quantity
   taken, as a mental abstraction, in its natural state, i.e., without
   being united with matter. (51)

Thus the substratum of quantitative change is not a definite quantity but matter with some quantity. Therefore, the destruction of definite quantity does not necessitate the destruction of the thing itself. 'The natural body' (al-jism al-tabi'i), composed of thing-ness and form, also preserves its species through the definite form (al-surah al-mu'ayyanah), which functions as the principle of its final differentia (al-fasl al-akhir)'. (52) Thus it is concluded that no kind of qualitative or quantitative change leads to the destruction of a physical body as long as the definite form endures. (53)

Change and Identity in Physical Bodies

After securing the material existence of physical bodies when they undergo substantial change, Sadra proceeds to the most important and intricate part of his theory of substantial motion, which is the preservation of the identity of changing bodies. Reference was already made to the fact that differentia (al-fasl), by definition, ensures the preservation of some quality or quantity-in-general despite the fact that the definite quality in the changing body is destroyed at every successive phase of its motion. Sadra states that whatever has the final differentia as its principle of perfection has some sort of preservation-in-general. The redefinition of differentia as a thing's principle of perfection becomes a forceful argument for Sadra because he seeks to replace the framework of traditional genus-differentia account with his gradational ontology. The differentia is now transformed from being a mere principle of difference (al-ikhtilaf) among genuses into a principle of existential individuation of particular entities. An important outcome of this reformulation is that differentia, viz. the principle of diversity and unity, is equated with being (al-wujud). Sadra illustrates this point as follows:

   Being capable of growth (al-nami) is the plant's differentia whereby
   its being is perfected, since its perfection is not due to its being
   a body alone. Rather, it (i.e., 'being capable of growth') is its
   principle of potency and carrier of its potentiality. Hence, there
   is no doubt that the change of bodily entities does not necessitate
   change in the substantial being of the plant itself since body is
   regarded here only in a general manner ('ala wajh al-'umum
   wa'l-itlaq), (i.e., as body-in-general), not in a specified and
   determined manner ('ala wajh al-khususiyyah wa'l-taqyid) (i.e.,
   not as body-in-particular). The same holds true for the animal which
   is constituted by being capable of growth and perception, and for
   every existent whose existence is constituted by matter and form
   such as man in relation to his soul and body. Hence when 'being
   capable of growth' changes in quantity, its 'thing-ness'
   (jismiyyatahu) as an individual entity also changes but its
   substantial structure as an individual entity remains the same. Thus
   it (i.e., the plant), insofar as it is a natural body-in-general, is
   destroyed as an individual entity, but, insofar as it is a natural
   body capable of growth, is not destroyed, neither itself nor even
   its part. Because every being part of which is nothing but
   body-in-general in an individual (entity) is established
   (in the external world) in a manner of continuous existence
   (al-ittisal al-wujudi). On the basis of this principle, the
   endurance of an animal together with its substance of perception can
   be explained. In the same manner, man in his old age loses most of
   his power of vegetation whereas his identity remains the same. (54)

The foregoing description of qualitative and quantitative change holds true for all natural bodies that have a constantly changing being with an enduring identity. In every change and motion, there remains an original principle that is perfected by the final differentia. For example, the final differentia in composite beings comprises every successive phase of increasing perfection, which intensifying or moving bodies undergo. Therefore, the succession of various degrees of being, which leads physical bodies to a higher state of being, is not something added to the final differentia of corporeal bodies from outside. As we have stated before, a simple being (basit al-haqiqah) contains in itself all lower levels of being, and this principle is employed here by Sadra with full force to explain the peculiar relationship among species, genuses, and differentia. Within this framework, every species comprises in its state of being whatever is possessed and shared by lower species. Equally important is the fact that species is perfected into a genus by differentia. The main point, however, is that Sadra takes differentia not simply as a mental notion abstracted from physical entities as the principle of differentiation but equates it with being (wujud), which functions, as we have seen, as the principle of unity as well as diversity in Sadra's ontology. (55)

The existential relationship between a physical body and its essential properties, or what Sadra calls 'concomitants' (lawazim), can also be explained by having recourse to the description of things in our ordinary language. When we want to define or describe something, we naturally refer to its essence as well as its essential properties that are included in its definition. Sadra calls such properties 'a mode of being' (nahw al-wujud). In every mode of being, a particular piece of concrete reality appropriates and displays certain qualities that yield its 'derived differentia' (al-fasl al-ishtiqaqi). These distinctive qualities are generally called the 'individual properties of a thing' (al-mushakhkhasat). They constitute what Sadra calls the 'signs of particularization' ('alamat li'l-tashakhkhus). Here is how Sadra summarizes his view:

   The (word) sign here refers to the name of a thing by which its
   concept is expressed. In the same manner, the derived real
   differentia (al-fasl al-haqiqi al-ishtiqaqi) is described as logical
   differentia (al-fasl al-mantiqi) in the case of 'being capable of
   growth' (al-nami) for plants, sense perception for animals, and
   intellection for human beings. The first of these (descriptions) is
   a name for the vegetative soul, second for animal soul, and third
   for rational soul. These are all derived differentia. The same holds
   true for all other differentia with regard to composite substances
   (al-murakkabat al-jawhariyyah). Each of these (bodies) is a simple
   substance designated by a universal logical differentia (fasl
   mantiqi kulli) as a matter of naming things (tasmiyat al-shayb).
   These substances are, in fact, simple and specific (i.e.,
   particularized) beings with no quiddity.

   In the same manner, the concomitants of individual entities are
   assigned to their individual possessors through naming. Thus,
   particularization is a mode of being. A particular entity becomes
   particularized by itself, and these concomitant (properties) issue
   forth from it just like the emanation of a ray of light from its
   source and of heat from fire. (56)

The logical differentia as a universal refers to entities in the order of mental concepts whereas the real or existential differentia refers to their individuation and particularization (al-tashakhkhus) in the order of being. At the conceptual level, we distinguish between a thing and its existential properties and thus obtain the essence-existence bifurcation. We apply such a conceptual process only 'to name a thing'. In reality, however, there are only individuated concrete existents, simple and unique, without requiring any 'quiddity'. Particularization of a thing comes about by its assuming a mode of being with certain essential properties (al-mushahkhkasat). In other words, the relation between a body and its existential properties is reversed: a physical body does not become particularized due to appropriating such essential and/or accidental properties. On the contrary, these properties come into being as a result of thing's particularization in the existential order just like the expansion of a beam of light from its original source of light.

Several conclusions can be drawn from Sadra's arguments. First of all, substance (jawhar) changes in accordance with the change of its essential properties. With this, the dividing line between substance and accident becomes rather provisional. A material substance is thus essentially

   a substance that is by itself continuous, quantified, positional,
   temporal, and inhering in a definite place. The change of
   quantities, colors and positions of the substance necessitates the
   renewal of the definite quantity of the individuated material
   substance. (57)

Thus, we arrive at a twofold picture of the natural world in which 'material substances' or 'bodily natures' are aptly regarded as the proper locus of two interrelated dimensions of physical entities: transience and perpetuity.

   There is no doubt that every material substance has a continuously
   changing nature on the one hand, and an enduring and unchanging
   structure, on the other. The relationship between the two aspects is
   similar to the relationship between body and soul. While the body is
   in constant change and flow, the human soul endures because it
   preserves its identity by the passing of essential forms in an
   uninterrupted continuous process (wurud al-amthal 'ala'-ittisal).
   (58)

Natural forms of material substances share similar characteristics:

   They are renewed at every instant as far as their material,
   positional, and temporal existence is concerned, and there is a
   gradual and steady origination for them. As far as their mental
   existence and detached Platonic forms are concerned, however, they
   are eternal and perpetual in the knowledge of God. (59)

As this paragraph makes it clear, Sadra locates the enduring and disembodied forms of natural substances within the eternal realm of Divine knowledge. (60) At this point, Sadra's notion of the great chain of being (da'irat al-wujud) comes full circle, and the main dialectical assertion of Sadrean natural philosophy that the order of nature is both self-subsistent and dependent upon the First Cause is stated one more time.

Concluding Remarks

Sadra's highly complex and original theory of substantial motion yields a number of important results. First of all, Sadra does away with the Aristotelian notion of a solid substratum as the basis of change and renewal in the world of corporeal bodies. Instead, he resolves the realm of physical bodies into a 'process of change' by introducing the notion of change-in-substance. The world of nature thus becomes a scene for the interplay of contingencies while preserving its 'substantial' unity and integrity. At this juncture, Sadra's concept of change as an existential property of things not only disregards Kalam atomism but also challenges the opaque world-picture of the Peripatetics. It must now be clear that substantial motion as articulated by Sadra is essentially different from the Peripatetic formulations of generation and corruption. Whereas the latter conceives change as an event of destruction and/or 'coming into being', the former defines change as a process of gradual intensification or diminution in modalities of being. It is also clear that Sadra posits substantial motion as an intrinsic property of things, material and immaterial alike, and envisages a world-picture that is in constant flux on the one hand, and directed towards a universal telos, on the other.

As we would expect, Sadra makes a profuse use of the concept of substantial motion and applies it to a number of philosophical problems. The relation between the changing (al-mutaghayyir) and the permanent (al-thabit), i.e., God and the world, origination of the soul from the body, i.e., the Sadrean doctrine that the 'soul is bodily in its origination and spiritual in its survival' (jismaniyyat al-huduth ruhaniyyat al-baqa'), and the rejection of the transmigration of souls (tanasukh) are only a few among the philosophical problems that Sadra reformulates in light of his concept of nature and motion-in-substance. In this regard, the implications of Sadra's natural philosophy go far beyond the confines of our present study. It is, however, clear that Sadra conceives change and permanence, the two interdependent aspects of the order of nature, as modes of being (anha' al-wujud). It is the all-encompassing reality of being (wujud) that connects together the cosmos from celestial spheres to animals and minerals. It is also the same reality that establishes an inexorable relationship between Sadrean physics and metaphysics.

(1.) Depending on the context, the word al-quwwah can also be translated as 'potency', and I shall do so here when Sadra uses the word in the sense of 'faculty' and 'ability to do something'.

(2.) Ibn Sina, Kitab al-Najat (ed. 1985), by Majid Fakhry, Manshurat Dar al-Afaq al-Jadidah, Beirut, p. 250.

(3.) Aristotle, Physics, Book VII, 241b.

(4.) Ibn Sina, al-Najat, pp. 145-6.

(5.) Sadr al-Din al-Shirazi (Mulla Sadra), al-Hikmat al-muta'aliyah fi'l-asfar al-arba'at al-'aqliyyah (ed. 1981), by M. Rida al-Muzaffar, Dar al-Turath al-'Arabi, Beirut, vol. III, Part 1, pp. 3-5. (cited hereafter as Asfar)

(6.) Sadra cites six different types of 'agency' (al-fa'il) in so far as the movement of things is concerned. These are "by intention" (bi'l-qasd), "by providence" (bi'l-'inayah), "by consent" (bi'l-iradah), "by nature" (bi'l-tab'), "by coercion" (bi'l-qasr), and "by force" (bi'l-taskhir). Cf. Asfar, III, 1, pp. 10-3.

(7.) Ibid., p. 6. Cf. also Sadra (1377 A.H.), Huduth al-'alam, 2nd edition Intisharat-i Mawla, Tehran, pp. 195-9.

(8.) Ibid., p. 20.

(9.) Before Sadra, this idea was stated also by Abu'l-Barakat al-Baghdadi. Baghdadi claims that since such terms as gradual and sudden are more evident and comprehensible to our common sense, we can easily understand the meaning of motion by employing such time-related terms. He thus sees no harm in using these terms in defining motion notwithstanding the seeming circularity. Cf. his Kitab al-Mu'tabar, (Hydarabad, 1357 AH), vol. II, pp. 29-30.

(10.) Asfar, III, 1, p. 23.

(11.) It is important to note, albeit briefly, that Sadra developed his concept of substantial motion against the background of the traditional theories of motion as expounded by Peripatetic philosophers, Kalam thinkers, and Illuminationists (ishraqiyyun). I shall discuss the views of the philosophers and the School of Illumination when analyzing Sadra's criticisms. As for the Kalam views of motion, I can only refer the reader to some traditional sources for further discussion. The Kalam views of motion are anchored in the central doctrine of atomism shared by the majority of Asha'rites and Mu'tazilites. Since the theologians conceived atoms as essentially indivisible and immutable, they were bound to define both qualitative and quantitative change as different compositions and combinations of the essentially unchanging atoms. This entails that change and motion come about only in the alteration of the accidental attributes of atoms, not in their essential constitution, thus reducing change to a system of external relations. To that effect, the Mu'tazilites developed the doctrine of 'kawn', i.e., 'to be present in a place' or 'to exist in a position in concreto'. According to this view, atoms always 'exist' (kain) in a particular location. Motion is therefore nothing but an atom's being (kain) in one position after having been in another. This makes motion an accidental property of atoms. Consequently, change and motion in the essential structure of atoms is rejected unanimously by Mu'tazilites and Ashcarites alike. In the same way, change or motion is allowed only in four categories: 'where' (ayn), 'position' (wad'), 'quantity' (kam), and 'quality' (kayf). Any change in the category of substance is denied on the ground that this would lead, as Ibn Sina and Suhrawardi had also argued, to the dissolution of the original substance. Cf. Khayyat (1957), Kitab al-Intisar, al-Matba'ah al-Katulikiyyah, Beirut, p. 32 ff.; al-Shahrastani, M., al-Milal wa al-nihal (ed., 1961), by M. S. Ghaylani, Sharikat wa Maktabat Mustafa al-Halabi, Cairo, p. 50 ff.; al-Baghdadi, 'Abd al-Qahir (1988), al-Farq bayn al-firaq, Maktabat Ibn Sina, Cairo, p. 101 ff.; al-Razi, Fakhr al-Din, al-Mabahith al-mashriqiyyah (ed., 1990), by M. al-Baghdadi, Dar al-Kitab al-'Arabi, Beirut, vol. I, pp. 671-793; al-Taftazani, Sharh al-maqasid (ed., 1989), by A. Umayra, 'Alam al-Kutub, Beirut, vol. II, pp. 409-59; al-Tahanawi, Muhammad, Kashshaf istilahat al-funun (ed.,1998) by A. H. Basaj, Dar al-Kutub al-'Ilmiyyah, Beirut, vol. I, pp. 462-73; Mahmud, Ali b. Ahmad b., "Risalah fi bahth al-harakah" in Collected Papers on Islamic Philosophy and Mysticism (ed. 1971), by M. Mohagheghn and H. Landolt, Tehran University Press, Tehran, pp. 35-51; and Frank, Richard M. (1978), Beings and Their Attributes: The Teaching of the Basrian School of the Mu'tazila in the Classical Period, State University of New York Press, Albany, pp. 95-104.

(12.) Cf. Aristotle, Physics, Book III, 201, 10: "The fulfillment of what exists potentially, in so far as it exists potentially, is motion".

(13.) Asfar, III, 1, p. 23.

(14.) Cf. Frank (1978), p. 100.

(15.) Asfar, III, 1, p. 26.

(16.) Sadra replies to al-Razi's doubt about the real existence of the passage-view of motion (qat') by relying on his teacher Mir Damad who holds that if a thing's being a continuous process as a whole or a unity is impossible, it should be impossible both in the mind and in the outside world. The possibility of the objective existence of the passage is "shown by a body extended in space where its parts are continuous and yet the whole also is given." Cf. Rahman, Fazlur (1975), The Philosophy of Mulla Sadra, SUNY Press, Albany, p. 95. In the process of time, a particular time-instant is followed by another. In the same way, one part of a moving body is followed by another in space. Since "a thing's existence as a whole in a time-instant is different from its existence in time, this thing may exist (as a whole) in time but its existence or some part of it (as a whole) cannot exist in a time-instant (an)". A moving body's being a present whole in a time-instant results not in motion but immobility. Sadra further stresses the point that this moving body as a whole may exist in time but not in a particular time-instance. The idea of gradual passage does not contradict a thing's being a whole or unity "because motion, time and the like are of the things that have weak existence (da'ifat al-wujud), every part of which contains the other's non-existence". Likewise, the 'gradual' passing is not negated by a thing's being a continuous single unity in time because time itself is nothing but a continuous single unity (amr muttasil wahid shakhsi). Cf. Asfar, III, 1, p. 28.

(17.) Asfar, III, 1, p. 33. Interestingly, in his note on the same page, Sabzawari rejects Sadra's criticism and insists on the subjectivity of the passage motion.

(18.) Ibid., pp. 33-4.

(19.) Ibid., p. 37.

(20.) Ibid., p. 40.

(21.) Ibid., pp. 39-40.

(22.) Ibid., pp. 41-2.

(23.) Ibid., pp. 47-8. Even though Ibn Sina seems to approve this view in essence, he uses the word nature (tabi'ah) in the sense of 'natural inclination' and natural motion rather than as an essential quality of corporeal bodies that render all volitional and coerced movement possible. Cf. al-Najat, p. 146.

(24.) Ibid., p. 49.

(25.) Ibid., pp. 48-9.

(26.) Cf. Aristotle, Physics, Book III, 200b.

(27.) The theory of latency was developed by the Mu'tazilite theologian Nazzam to explain origination and corruption (kawn wa fasad). Nazzam who, unlike most of the Mu'tazilites and the Ash'arites, had rejected atomism, presupposes a potential nature that is 'latent' in things and that becomes 'apparent' in time. Therefore, he regards any kind of change as the appearance (zuhur) of these dormant qualities. Cf. al-Khayyat, Kitab al-Intisar, p. 28ff.

(28.) Asfar, III, 1, pp. 57-8.

(29.) Asfar, III, 1, p. 58.

(30.) Rahman (1975), pp. 95-6.

(31.) As I stated before, nature, like matter and form, is not a thing but a principle of existentiation and substantiation (tajawhur).

(32.) Asfar, III, 1, p. 62. See also Kitab al-Masha'ir trans. by Henry Corbin (1968) as Le Livre des penetrations metaphysiques, Institut Francais d'Iranologie de Teheran, Teheran-Paris, pp. 64-5.

(33.) Asfar, III, 1, pp. 61-4.

(34.) Ibid., p. 65.

(35.) Sadra's criticism can be summarized as follows: The first phase is motion itself and the second is a thing's transposition from one point to another. According to this account, which is reminiscent of the passage view mentioned above, something always remains stable in the process of motion, and this is nature. A relationship of sorts is thus established between the stable which is nature and the changing which is a thing's passing through a certain distance. Sadra rejects this argument by restating the relationship between substance and accident: since substance is the source as well as locus of accidents, all accidental properties and changes should issue forth from substances. If there were no being whose very essence would be renewal and lapse, there would be no stages of motion. For Sadra, the weakness of this argument lies in the fact that a thing's changing its place from one point to another, which is regarded by the philosophers as the second stage in the process of motion, is not essentially different from motion itself. Therefore, both kinds of change are due to that 'reality whose essence is continuously changing in itself', and this is what we called "nature". But since the 'mental substances' are beyond the realm of existential transformation, they always remain stable and unchanged. This is also true, says Sadra, for the human soul which, from the point of view of its 'mental essence' or 'reality', is changeless, but from the point of view of its connection with the body, it is identical with continuously changing nature. Thus the gist of Sadra's argument is that a continuously changing structure cannot depend on a stable cause. The renewal of all changing beings is due to a cause whose very reality is change and renewal at every moment. Asfar, III, 1, pp. 64-7.

(36.) Ibid., p. 68.

(37.) Ibid., pp. 68-9. Sadra explains this complementary duality of things on the basis of the gradation (tashkik) of being which is, for Sadra, both the principle of unity and diversity in existence.

(38.) Ibid., p. 72.

(39.) Ibid., p. 73. Sadra also states that if change in categories is not admitted, the opponent would be forced to adhere to the idea of 'leap' (al-tafrah) proposed by al-Nazzam. Sadra insists that the theory of leap is easily rejected by common sense.

(40.) Ibid., p. 74.

(41.) Ibid., p. 75.

(42.) For Ibn Sina's discussion of what he calls al-takhalkhul (diminution) and al-takathuf (augmentation), see al-Najat, pp. 186-8 and pp. 242-4.

(43.) Ibid., p. 89.

(44.) Ibid., p. 82.

(45.) Ibid., p. 83.

(46.) Ibid., p. 84; Rahman's translation, op. cit., p. 103.

(47.) Ibid., p. 86; Rahman's translation op. cit., p. 104.

(48.) Ibid., pp. 87-8.

(49.) Ibid., pp. 89-90.

(50.) Ibid., pp. 90-2.

(51.) Ibid., pp. 92-3.

(52.) Ibid., p. 93.

(53.) Ibid., pp. 80-93.

(54.) Ibid., p. 94.

(55.) Ibid., pp. 93-100.

(56.) Ibid., pp. 103-4.

(57.) Ibid., p. 104.

(58.) Ibid., pp. 104-5.

(59.) Ibid.

(60.) After providing a thorough analysis of substantial motion as an intrinsic quality of things, Sadra gives an interesting example of self-defense by emphatically rejecting the charge that his theory is an 'innovation'. It is God, the Sage of all sages, says Sadra, who has laid down substantial motion as the very essence of the world-order. To this effect, Sadra quotes a number of verses from the Qur'an, all of which allude to the difference between appears to be reality and the real state of affairs in the world-order that can be grasped only at a higher level of consciousness. These verses also attest to Sadra's attempt to align his cosmology with that of the Qur'an: And thou seest the hills thou deemest solid flying with the flight of clouds: the doing of Allah Who perfecteth all things (Q. 27: 88). On the day when the earth will be changed to other than the earth, and the heavens (also will be changed (Q. 14: 48). That we may transfigure you and make you what ye know not (Q. 56: 61). In addition to the Qur'anic verses, Sadra also quotes from 'Ali ibn Abi Talib's Nahj al-Balaghah, which points, once again, to Sadra's desire to construe the intrinsic-existential transformation of things as a religio-cosmological doctrine. Cf. Kitab al-masha'ir, pp. 66-7.

Ibrahim Kalin is Assistant Professor, Department of Religious Studies, College of the Holy Cross, 1 College Street, P.O. Box 78A, Worcester, MA 01610, USA; Email: [e-mail].