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Gifted Students and Philosophy: The Sound of a Tree Falling in the Forest ...

Groans might greet anyone posing the question, "If a tree falls in the forest with no one around, does it make a sound? This venerable poser is, however, laden with philosophical intrigue. In fact, the issues that this question raises typically tantalize gifted students (indeed, anyone with a serious interest in philosophy) and for two reasons. First, the questions, although immediately relevant to certain basic forms of personal experience, are difficult to answer satisfactorily, doubtless because, second, the questions revolve around issues that go straight to the core of a particularly fundamental region of philosophical reflection.

Earlier discussions in this series devoted to philosophy and gifted students have included Plato's concern for establishing theoretical grounds to show how we have knowledge and St. Augustine's thoughtful and penetrating inquiry into the nature of time. These two classic questions illustrate the areas of philosophy known as epistemology and metaphysics, respectively. Epistemology addresses questions and problems pertaining to knowledge and how human beings obtain it; metaphysics discusses the nature of reality (e.g., time) in general and abstract terms.

When philosophy is pursued as an ordered discipline, these areas are typically kept separate from one another in order to keep the analysis of their problems within manageable bounds. However, the question, whether or not an unperceived tree falling in the forest makes a sound, effectively intersects these two areas, especially if that question is approached from the standpoint of the Irish philosopher George (Bishop) Berkeley (1685-1753). Berkeley's account undercuts this distinction by showing how questions pertaining to knowledge play directly into questions pertaining to the nature of reality. Here then metaphysics implies epistemology and vice versa.

With Berkeley (pronounced "BARK-lee," as in Charles Barkley, former NBA great) we are squarely within the modern period of philosophy. "Modern" philosophy is usually dated to begin with the work of Rene Descartes (1596-1650). Descartes' quest to establish the same type of certainty in philosophy, which he saw, and contributed to himself, in the sciences and mathematics, inaugurated an extended period of intense philosophical reflection on the nature of human knowledge. Descartes' answer to the basic question of knowledge--that certainty derives from the self and how we experience and understand our ideas--was deemed inadequate by many of his philosophical successors, primarily John Locke (1632-1704). Locke, as an empiricist, insisted that the materials of knowledge originated from outside the mind and were processed and made meaningful by the mind.

George Berkeley, usually referred to as Bishop Berkeley (he was a prelate in the Anglican Church), continued to think about knowledge along these lines. In a work entitled "Three Dialogues Between Hylas and Philonous," Berkeley extended Locke's empiricism in an unusual and distinctive direction. Few philosophers after Plato wrote dialogues since they did not want to be seen trying to compete with Plato in expressing difficult ideas in a literary form of which the great Greek master was the exemplar. Berkeley is an exception, however, and in this work he presented a series of short dialogues between two fictional characters with etymologically significant names: "Hylas" is from the Greek for "matter" while "Philonous," also Greek, means "lover of mind or spirit." Thus, the dialogues recorded a conversation between, in essence, matter (Hylas) and spirit (Philonous). The three excerpts cited below present key representative statements of Berkeley's overall position.

Preliminary Discussion

Pose the question, "If a tree falls in the forest with no one around, does it make a sound?" As noted above, this question may seem banal but, in my experience, students nonetheless find it fascinating with discussion of the question quickly becoming energetic and, at times, somewhat heated. Have the students discuss their answers and allow discussion to continue for a few minutes, inviting students to critique the reasons given by those arguing for each side of the issue. Then conclude this discussion by wondering out loud whether there might be a third answer to this question, an answer other than yes or no. (There is such an answer, as we shall see.)

Now modify the original question by posing the following variation: "Does a tree in the forest continue to exist if no one is around to see it?" The typical response is immediate and forceful--"Of course the tree continues to exist!" Gifted students believe they discern a clear distinction between (a) the existence of the tree when no one is around and (b) the sound a tree might, or might not, make if it falls when no one is around. The existence of the tree is more fundamental than a sound a tree might make. Therefore existence is less dependent upon a human observer than sound. In fact, students nearly always assert that the existence of something does not in any sense require an observer in order to guarantee that thing's existence.

But, Berkeley asks, how do we know that this claim about the unperceived existence of the tree is true? Why can we be certain that a tree in a forest continues to exist if no one is there to perceive it as existing?

The following excerpts from "Three Dialogues" present a reasoned account that answers this question. (Suggestion: Have the students "perform" these excerpts, with a different Hylas and Philonous taking their parts for each of the three passages.)

Passage 1--The Definition of "Sensible"
   Hylas: I tell you once for all, that by sensible things I mean those only
   which are perceived by sense; and that in truth the senses perceive nothing
   which they do not perceive immediately, for they make no inferences....

   Philonous: This point is then agreed between us--that sensible things are
   those only which are immediately perceived by sense.


The key concept in this passage is the meaning Hylas gives to "sensible things." In non-philosophical contexts, the word "sensible" is often used to refer to human conduct, as when teacher intones to a student "please act in a sensible manner." Here Hylas brings out the root meaning of the term (i.e., what is "perceived by sense"). Hylas also adds the important characteristic that the senses function immediately, or, as he puts it, the senses "make no inferences." This last point may be demonstrated. Hold up a piece of chalk (or marker, etc.). Ask "What color is this?" The students will chorus an answer (e.g., white). Then ask, "Can you tell what this object feels like just from seeing its color. Occasionally someone will blurt out "Hard!" but this response is unthinking. Someone who sees a piece of chalk and who has also held a piece of chalk can remember what the chalk feels like, but they cannot see what the chalk feels like. If we hold a piece of chalk, we feel its hardness but if we just see a piece of chalk, there is no way, just from the sense of sight alone, we can infer that this white object is hard. The following queries usually succeed in making this point, and the students find the sequence of thoughts intriguing: If you close your eyes and someone hands you a piece of chalk, can you tell what color it is? No. If you see an object without touching it, can you tell what it feels like? No. From what is seen, we cannot infer touch; from touch, we cannot infer what is seen. Thus, in Hylas' words, the senses "make no inferences."

This definition of "sensible" establishes the meaning of a concept that will become important later in the discussion. It is fairly common in philosophy to state and describe a definition and then hold that definition in reserve until it is needed later in the development of a given position; such is Philonous' strategy in eliciting the definition of "sensible" from Hylas at this point. In general, this brief interchange brings out the distinction between what we perceive and what we know. We perceive that the object is white, but we know that this object (a) is a particular piece of chalk, which (b) is hard, and (c) is capable of being used as a tool for writing based on what perception has taught us and also what our minds have added to perceptual data through memory and reasoning. In analyzing the nature of knowledge, it is essential to keep processes such as perception and knowledge separate from one another as much as possible to clarify the structure of each of these components and to be aware of questions and problems that might arise as a result of such clarification.

Passage 2--Thinking and Its Object

Before the students read this passage, remind them of the question discussed earlier about whether a tree exists if no one is perceiving or thinking about it.
   P: The tree or house therefore which you think of is conceived by you?

   H: How should it be otherwise?

   P: And what is conceived is surely in the mind?

   H: Without question, that which is conceived is in the mind.

   P: How then came you to say, you conceived a house or tree existing
   independent and out of all minds whatsoever?

   H: That was I own an oversight; but stay, let me consider what led into
   it--it is a pleasant mistake enough. As I was thinking of a tree in a
   solitary place, where no one was present to see it, methought that was to
   conceive a tree as existing unperceived and unthought of, not considering
   that I myself conceived it all the while. But now I plainly see that all I
   can do is to frame ideas in my own mind. I may indeed conceive in my own
   thoughts the idea of a tree, or a house, or a mountain, but that is all.
   And this is far from proving, that I can conceive them existing out of the
   minds of all spirits.

First a small procedural point. Students reading this passage occasionally hesitate over "methought," a locution that appears to be a linguistic leftover from the days of Robin Hood. Recall, however, that we are reading English from the early 18th century, and students may be reminded of the fact that living languages continually evolve over time, with individual words and turns of phrase coming in and going out of fashion. (As an aside, methinks that "methought" in a work of philosophy is thoroughly charming.)


Ask the students: Do you believe that things exist outside the mind? Of course, they will say. Then ask them this, a more challenging variation on the same question: When they think of things existing outside of the mind, do these things exist apart from the act of thinking about them? The answer, after a bit of reflection, will be yes, since it is in effect the same question. Now take a particular thing--say, a tree existing in a solitary place. Does the existence of this tree depend on our thinking about that tree existing in a solitary place? The students will say, no, it does not. But Philonous wants to know how one can claim that the tree is existing alone and unperceived if this tree is being thought of as existing unperceived and alone? For surely the thinker remains in the company of that tree insofar as the thinker is in the act of thinking about it. Therefore the tree is not alone and unperceived; it is, in fact, being thought of by someone as alone and unperceived. How then does the individual thinking this thought know for certain that this tree will continue to exist if one does not think about it at all?

To think or conceive of a tree existing alone in the forest is to have that tree in one's mind, even if the original intention was to isolate that tree--in your mind--so that no one is around to perceive it or to think about it. It seems inescapable then that all we can have in our own minds are ideas of things, and that it is not possible to conceive of things existing out of all minds, whether my own mind or anyone else's.

Passage 3-- Scepticism and the "External" World

This passage leads to the primary philosophical conclusion and also effectively answers the lead question concerning the tree falling in the forest.
   P: But how can that which is sensible be like that which is insensible? Can
   a real thing, in itself invisible, be like a color, or a real thing, which
   is not audible, be like a sound? In a word, can anything be like a
   sensation or idea, but another sensation or idea?

   H: I must own, I think not.

   P: Is it possible there should be any doubt on the point? Do you not
   perfectly know your own ideas?

   H: I know them perfectly; since what I do not perceive or know can be no
   part of my idea.

   P: Consider, therefore, and examine them, and theft tell me if there be
   anything in them which can exist without the mind: or if you can conceive
   anything like them existing without the mind.

   H: Upon inquiry, I find it is impossible for me to conceive or understand
   how anything but an idea can be like an idea. And it is most evident that
   no idea can exist without the mind.

   P: You are therefore, by your principles, forced to deny the reality of
   sensible things; since you made it to consist in an absolute existence
   exterior to the mind. That is to say, you are a downright sceptic. So I
   have gained my point, which was to show your principles led to Scepticism.

   H: For the present I am, if not entirely convinced, at least silenced.


Ask the students: "Who won this exchange?" Those who have been paying attention to the rhythm of thought will say "Philonous!" Hylas does not exactly cede the point at issue, but he does admit that he cannot think of anything to say in response to Philonous' reasoning. What then has the reasoning demonstrated? Consider the following summary of the passage:

A. Philonous asks us to consider a real thing, such as a tree. Is this tree "audible," that is, does it produce a sound? Not as such, that is, not as a tree. But, sound is, by itself and necessarily, audible. Therefore, if sound when sensed is something perceived, then how can something that is not audible (e.g., a tree) even be like such a sensation? Philonous insists that there is no basis of comparison that will allow us to connect the perception of sound with something that, by itself, is without sound.

B. We know the ideas we have based on whatever we perceive. If I do not perceive something, then what I do not perceive cannot be part of my idea of that something. Therefore, only an idea can be like another idea, in the same way that only something perceived can be like something else perceived. The question then becomes whether an idea (e.g., of a tree) existing in our mind can be like the "real" tree existing "outside" our mind.

C. Hylas had said that reality was "sensible things," things that existed absolutely outside of the mind, just as we might say that the tree outside the window exists absolutely apart from, or outside of, the mind of an observer (or observers) seeing the tree. The relevance of the definition of "sensible" given in Passage 1 now emerges. Sensible things are things immediately perceived by the senses. When what is perceived by the senses strikes the mind, the sensory experience produces an idea. But, ideas derived from sensible experience exist only in the mind. Furthermore, Passage 2 has shown that ideas resemble only other ideas--not what the ideas are ideas off Therefore, the question becomes: How do we make the transition from the idea of a tree that exists in our mind to the actual tree existing outside our mind?

Philonous' reasoning (based on Hylas' own stated principles) demonstrates that we cannot make such a move and be confident of any success. For if all that exists is only what is sensible, then we can never be completely certain that what is perceived through the senses really and in fact exists out there, "outside" our senses. We are reduced to a condition of skepticism about the existence of the sensible world. All we know, and apparently all we are capable of knowing, are our own ideas. According to Philonous, it is therefore impossible for us to assert with certainty that things outside our ideas actually do correspond to these ideas. We cannot get outside of the ideas we have in our minds in order to assert that material things exist apart from these ideas.


The general meaning of skepticism may have to be explained. One standard dictionary definition of skepticism is "the doctrine that the truth of all knowledge must always be in question." It should be emphasized that the skepticism of which Hylas is accused concerns not just a state of suspended belief about knowledge concerning this or that particular thing, but about the very "existence" of "all" sensible things. That is, everything that can be perceived by the senses, which is everything we see, touch, taste, and so forth. The skepticism, which arises at the end of the third excerpt, is therefore radical in the extreme. What we refer to as the "external world"--that vast ensemble of booming and buzzing this, that, and the other that exists "outside of" our senses--becomes, on Hylas' principles, a region of reality that enjoys at best a dubious existence.

Here is another way to approach the conclusion established at the conclusion of the three excerpts. To say "Something (e.g., a tree) is real" seems to assume the truth of the claim that "I know that this tree is real." For if something were real, but we could not know this something, then by what right do we assert that this something is real in the first place?

This philosophical priority is reflected in ordinary situations whenever someone says "How do you know?" as a response to a claim. A question about the origin or justification of knowledge usually refers to a claim that appears dubious or, perhaps, controversial. But in theory, "How do you know?" could preface every claim anyone has ever made. If I say "There's a tree outside," I must be willing to answer the question "How do you know?" As a rule, people in civilized society would not pose such a seemingly uncivil question about routine perceptual observations--assuming, of course, that the senses of the parties involved are all functioning properly-because it is "obvious" that the claim refers to something that truly exists. But, such existence is "obvious" only because everyone involved in the discussion sees a particular sensible object--or, as Berkeley might put it--we think we see a particular object.

Berkeley's position may be summarized as follows--"to be is to be perceived"--the Latin version of this principle--esse est percipi--being almost as well known in philosophical circles as Descartes' cogito ergo sum (I think, therefore I am). This position is sometimes referred to as absolute idealism, since it requires that a mind must exist and function as a mind thinking about things before anything else can be said to exist. In a sense then, the mind "holds" all existing things within it insofar as human beings perceive and think about these things. Without such perception and thought, the existence of "external" objects becomes uncertain.

This position has noteworthy and, it must be said, decidedly unusual consequences. Ask the students the following three questions:

1. If all human beings were asleep, what would happen to the earth?

2. If all human beings vanished, what would happen to the earth?

3. If every living thing that can perceive and think vanished, what would happen to the earth?

The common-sense answer to (1) is "Nothing would happen to the earth." Common sense also dictates the same answer to (2) "Nothing would happen to the earth." And since (3) is just a more precise version of (2), then the answer to (3) is identical to the answer to (2) "Nothing would happen to the earth." But, if Berkeley's reasoning is correct, then the answer to all three questions is the same--"We don't know what will happen to the earth." And the reason we don't know is because, as the reasoning of Hylas and Philonous has demonstrated, to be is to be perceived. If, therefore, something is not perceived, the best we can do is to be skeptical about its actual existence apart from a mind perceiving that thing.

Once this conclusion has been established, ask the students the original question-- "If a tree falls in the forest and no one is around, does it make a sound?"--and have them state the answer that can be inferred from Berkeley's principles. The answer is ... "We don't know." Whether or not the falling tree will make a sound without an observer present to hear that sound cannot be determined. Thus, the venerable tree-in-the-forest-question admits of more than a "yes" or "no" answer; the third possible answer is the answer of the skeptic--"We do not know." In general, then, Berkeley's reasoning has shown the close intimacy between metaphysics and epistemology--that what we believe to be reality depends directly on what we actively perceive when in the presence of this reality.

This conclusion is important, fascinating, and well worth serious and sustained philosophical reflection. But, aside from the definite possibility of inciting some intriguing and doubtless volatile classroom discussion about perception and existence, both of which are decidedly abstract philosophical concerns, does Berkeley's thinking carry with it any practical pedagogical relevance?

Thoughts on Curricular Integration

Previous installments in this series have offered specific suggestions for integrating aspects of the philosophical positions discussed into a more standard school curriculum. Since, however, the intimate connection between perception and the existence of things is developed with considerable generality in Berkeley's thought, the most fitting curricular application is perhaps not to any particular subject, but rather to an attitude that can affect the way gifted students approach many subjects, as well as, in a larger sense, certain important areas in life outside the classroom. This attitude is the "skepticism" that often characterizes young students, gifted and nongifted alike.

The Specter of Skepticism

Skepticism appears in a variety of educational contexts: For present purposes, consider skepticism in the attempt to gain knowledge of a poem. Thus, why are the results of an experiment in science not subject to the kind of skepticism that affects (or, perhaps, infects) the interpretation of a poem (or, of course, any literary work), where discussion so quickly and so often reduces to "That's your opinion," or even, "Well, no one can say what the poem really means?" Ask the students in a language arts class: Can we know the meaning of a poem in the same way that we can know the meaning of an experiment in science? Or, more generally stated: How is objectivity possible when doing a scientific experiment in contrast to the apparently unavoidable subjectivity that prevails when interpreting a poem? In fact, where does the supposed "objectivity" of science come from in the first place?

It is relevant at this juncture to observe that the clear distinction between the "objective" reality of scientific study and the "subjective" values of literary criticism cannot be maintained within Berkeley's thought. For Berkeley, whatever is "objective" is no less governed by the need to be perceived by the mind to guarantee its existence than is whatever may be only "subjective." What elements therefore in scientific investigation allow us to conclude that the results of such thoughtful activity have indeed put us in touch with its subject matter--the "objective" physical world?

Scientific experiments depend on observation and can be repeated by other individuals to verify observable results; as a result of these and related considerations, we believe that science places those who practice it directly within a public and commonly shared world. Reading and interpreting a poem is, by contrast, a private activity, and since such interpretation produces results that exist entirely in the realm of "meanings," whatever results are produced do not enjoy the status of the perceptible and public shared reality that encompasses the activities and practices of the scientist. But, consider the following line of thought: A poem is real, just as the material "stuff" that becomes subject to the scrutiny of science is real. If therefore a poem is taken to exist as an artifact, something made from a human source, then there seems to be no reason why students of a poem could not discuss the structure of this rhythmical bit of reality with a care and rigor that fits its subject matter and with expectations of producing concrete results that can be defended or amended, as the twists and turns of discussion and analysis so indicate.

A Berkeleyian Antidote to Skepticism

The point of these observations is not to transform the study of literature into a clone of scientific research--that would be neither possible nor desirable. Rather, it is to become aware of what would have to be done to reshape attitudes toward the study of literature (and other nonscientific subjects) so that students will not automatically be tempted to dismiss such study as so much personal and subjectivistic patter.

It is a singular virtue of reflecting on Berkeley's thought that it invites gifted students to question how they as individual human beings experience the world--and this includes, of course, the world of literature--in order to be in a position to discuss that experience meaningfully with others. For Berkeley, any form of inquiry presupposes the observer and whatever the observer contributes to that inquiry. Berkeley shows the need to pay attention to what is perceived and to describe it as accurately as possible so that other observers, hearing this description, can verify its sense through their own perceptual experience.

Gifted students frequent skepticism can therefore be diminished, or at least rendered less virulent in its effects on the educational enterprise, if gifted students learn to try to get "outside" themselves as much as possible--to move the mind from inherent concerns and preconceptions to the object of study, whether this object be a poem in language arts or an experiment in science. One effective way to achieve this transition is to maximize the amount and depth of discussion of whatever it is that gifted students are experiencing--and, of course, perceiving-thereby taking advantage of the fact that much of our experience of the world is shared with other human beings. The more we are aware of what we feel and think in relation to what others feel and think, the less insular and isolated we will become in studying what exists "out there" in the world.

Skepticism and Values

The skepticism affecting the study of certain subjects in a school curriculum also permeates one of the most important areas in life, both within and outside of school. Ask students in a language arts class whether cheating on an essay or exam is morally wrong. An answer that occurs all too frequently runs along these lines. Cheating is wrong for you if you feel, or believe, that it is wrong; if, however, cheating is a useful expedient to rectify lack of preparation for an assignment or test, then who's to say that cheating is wrong in these circumstances? And if cheating is an acceptable option in school, why shouldn't it also be viable later in life, in nonacademic situations?

Another route to the same destination: Ask a class of gifted students--"is honesty a good thing?" Most, perhaps all, will say yes. But, then ask, "Why is being honest a good thing?" Reasons and justifications will come quickly and be wide-ranging; however, what nearly always happens is that the reasons soon appear to conflict with one another and are also not developed sufficiently to answer objections based on concrete circumstances. The result is a creeping skepticism that begins to infiltrate the group perception of the value of honesty.

Facts are public and verifiable, values are private and variable depending on the person. The reality of values is defined by the limits of an individual's feelings and perceptions about his or her world; in fact, values simply are what that individual feels is an appropriate attitude or behavior in a given set of circumstances. This belief is very common among young people (it is also, of course, very common among adults). But, how reliable is this belief?.

As noted above in the context of skepticism and education, it is essential to determine the boundaries of the "I," that is, what I sense and perceive and think--the sum total of my own individual experience--and then place these boundaries in juxtaposition with what others sense and perceive and think. Our perceptual activity is in some important respect a social activity (i.e., what we see and experience as individuals has something essential to do with what we as members of a group have been conditioned to see and experience). What we then label "reality" insofar as it is emergent from this common source of experience is determined at least as much by our collective perceiving of what is "out there" as by whatever this reality may be "in itself" or "as such."

This conclusion about the close connection between the way we experience the world and the existence of the world as such has an essential bearing on the conclusions we wish to draw about our personal beliefs and values. Skepticism concerning moral values--happiness, goodness, justice, honesty and other forms of virtue--derives from the unexamined belief that we cannot move beyond our own individual conceptions, or perceptions, of the patterns and consequences of human behavior. Berkeley's thought invites us to reconsider this encrusted distinction that so permeates the fabric of contemporary life. From Berkeley's perspective, values and facts are suffused with personal experience. It follows then either that facts are no less personal than values, or that values may be considered to have as much solidity as facts--assuming that they are approached and described in a way that displays their existence in a world beyond that of an individual observer of human behavior. Thus, if I say "cheating is wrong," I must be willing to support that claim with reasons based, in some respect, on features of the world insofar as the world actually exists. As a result, a persuasive justification of honesty as a virtue will not be based merely on the fact that the speaker of this claim feels that honesty is something good or morally praiseworthy, but rather on perceived aspects of a common world that go beyond the fact that the speaker, as a single human being, approves of honesty.

The currently popular attempt to institute character education in schools is certainly laudable. But, with Berkeley's position in view, this attempt should be supplemented by inviting (and, perhaps, compelling) young people--whether gifted or nongifted--to examine the experiences they have had of the world, whether enjoyable, unpleasant, or indeterminately "blah," and to integrate this complex cycle as fully as possible with the closely similar experiences of other human beings. When such integration has been successful, then the understanding of values and the essential role they play in the development of character may be established on something more substantial than individual inclination. Thus, honesty, as one virtue among many, could then be established as a feature of the world defined by structures that incorporates a public sphere of considerations rather than simply asserted as a value on the strength of the individual attitudes of people who "feel" that honesty is morally praiseworthy.

In retrospect then, the apparent whimsicality of wondering whether or not unattended falling trees make sounds in forests takes on a very different and far more serious tone. For when, with Berkeley's assistance, we think through a philosophical answer to this chestnut, we appreciate more fully and urgently the central character of our individual experience of the world and the need to integrate that experience with all that encompasses "reality" and "value" as perceived and thought by those with whom we share our world.


Berkeley, G. (1995). Three Dialogues Between Hylas and Philonous. In S. M. Cohen (Ed.), Classics of western philosophy. (4th ed.). Indianapolis, IN: Hackett.

David A. White, Ph.D., teaches philosophy courses for Northwestern's Center for Talent Development and for the gifted programs of the Chicago Public Schools. He may be reached at 6608 N. Bosworth, Chicago, IL 60626.
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Author:White, David Gordon
Publication:Gifted Child Today
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Date:Jul 1, 2000
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