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Making room for stem cells: dissociation and establishing new research objects.

Embryonic stem (ES) cells represent the latest front in political battles over the "culture of life." President Bush and his supporters among religious conservative groups claim that ES cell research constitutes murder of developing life, while others--scientists, patient advocates, and politicians across the spectrum--view ES cells as potential cures for many diseases (Bush, 2001, 2005; Daley, 2004; Wade, 2003). The issue of ES cell research arose during the presidential debates and in state referenda during the 2004 election (Kasindorf, 2004; Mansnerus, 2005), and it took center stage again in May, 2005, when the House of Representatives voted to increase federal funding of ES cell research (Stolberg, 2005). The Senate passed this bill in the summer of 2006 (Hulse, 2006), and President Bush (2006) vetoed it the following day because, he said, it would "violate human dignity" ([paragraph] 2).

While appeals to medical benefits and the "culture of life" have become the stock topoi of the contemporary debate, they were not available more than 20 years ago, when ES cells in mice first were isolated; nor were they as powerful 8 years ago, when human ES cells first were isolated. The original attraction of ES cells was that they could illuminate the process of mammalian development from fertilized eggs. Yet, a different model for studying this process--embryonic carcinoma cells--already existed, and a third possibility--embryonic germ cells--was discovered about the same time as ES cells. Each cell type has the capacity to produce some, if not all, of the cells in a body's organs, enabling scientists to study the processes by which mammals develop. For this reason, all three cell types initially were called stem cells or stem-like cells (Gardner & Beddington, 1988; Smith, 2001).

Researchers working with ES cells needed to establish the unique value of their object of study. In order for people--scientists and nonscientists--to accept new objects and ideas produced by science, old concepts must be reorganized. This reorganization occurs through the use of real definitions. The practice of dissociation represents a paradigmatic linguistic means of creating real definitions. Dissociation takes a unitary concept and breaks it into two components, which receive positive and negative valences through the use of philosophical pairs of opposed value terms. This breakage creates space for new ideas and objects while addressing conflicts and contradictions that arise in one's worldview.

Current scholarship offers two views of dissociation. One treats dissociation as an intentional argumentative strategy, especially in politics (Zarefsky, 1980; Zarefsky, Miller-Tutzauer, & Tutzauer, 1984). The other treats dissociation as central to the creation of real definitions that determine what counts as reality in a language community (Goodwin, 1991; McGee, 1999; Schiappa, 1993, 2003). In this latter view, dissociation is implicit and unconscious as often as it is a deliberate, conscious choice (Schiappa, 1985). This essay seeks to integrate these two views by positing a continuum that extends from unassuming acts of real definition to intentional, strategic uses of dissociation. Implicit, unconscious acts of real definition in arenas like the technical sphere of stem cell research generate the grounds for strategic dissociations in political and policy debates.

Dissociation played a vital role in defining stem cell. Researchers who began working with ES cells 20 years ago needed to establish their value as a model of development: They needed to clear other models out of the scientific and rhetorical space known as model for development in order to make room for ES cells as the model of development. For ES cells to become this model, multiple dissociations needed to crystallize around these new research objects, shaping people's real definitions, their determinations of "appearance" and "reality." Establishment of ES cells as the path to understanding development opened up the possibility that these cells might be used to repair developmental and degenerative disorders, such as Parkinson's disease and Type I diabetes. Such medical applications, which have become the key justification for expanded ES cell research, are grounded in the prior real definitions that justify study of mammalian development via ES cells.

This essay will examine dissociation in the early scientific debate about embryonic stem (ES) cells. It begins by examining previous work on dissociation. It argues that the reality/ appearance pair that is central to dissociative real definitions depends on a psycho-social consensus of the world's "reality," and not on a naive philosophical realism. Next, the essay examines three dissociations that, collectively, reorganized the material and social space of science, dividing the category stem cell into embryonic carcinoma (EC) cells and ES cells, and establishing the grounds for future separation of embryonic germ (EG) cells and ES cells. Finally, the essay posits, dissociation is not only a form of arguing and defining; it also enables future argumentation (Stahl, 2002). The dissociations used to differentiate stem cells provide the basis for later strategic arguments about stem cell "potency" and the value of ES cells that are eligible for federal funding.


Many scholars of definitional argument focus on definition by dissociation, especially as it is used by political rhetors (Goodwin, 1991; McGee, 1999; Murphy, 2004; Schiappa, 2003; Stahl, 2002; Walton, 2001; Zarefsky, 1980; Zarefsky et al., 1984). Dissociation splits a concept into two components, one of which is seen to be more valuable than the other. The two new concepts are related hierarchically: one is "better" or "more realistic," the other is "worse" or "mere appearance." Adjectives may characterize one concept as a "claim" or "hypothesis," or a term may be placed in quotation marks to disqualify the concept (Perelman & Olbrechts-Tyteca, 1958/1969, p. 438). Dissociation may be implicit or explicit, conscious or unconscious (Schiappa, 1985). It "is always prompted by the desire to remove an incompatibility arising out of the confrontation of one proposition with others, whether one is dealing with norms, facts, or truths" (Perelman & Olbrechts-Tyteca, 1958/1969, p. 413), and clears conceptual and practical space for action. Ronald Reagan's definition of the "truly needy" exemplifies dissociation in action (Zarefsky et al, 1984). The word truly dissociates those with "real" needs from those with "apparent" needs, a dissociation that enabled Reagan to justify cutting welfare programs while still claiming to help those who need it.

According to Perelman and Olbrechts-Tyteca (1958/1969), dissociation "expresses a vision of the world and establishes hierarchies for which it endeavors to provide the criteria" (p. 420). These criteria are expressed in value-laden philosophical pairs, in which one term is preferred for metaphysical, ethical or other reasons tied to the pragmatic interests of those engaging in the dissociation (Perelman & Olbrechts-Tyteca, 1958/1969; Schiappa, 1985; Zarefsky et al., 1984). Some common philosophical pairs are accident/essence, means/end, good/bad, relative/absolute, particular/general and theory/practice. Rhetors also may construct new or ad hoc pairs, such as when the Supreme Court, in mid-twentieth century rulings about religious practices, dissociated the concept of interest into state and individual interests (Stahl, 2002).

Although many studies of dissociation have focused on political cases, dissociation also has scientific and technical uses. Scientific debates about the formulae used in an experiment can dissociate physics into Newtonian and quantum physics, where the latter and its associated formulae offer a more "complete" and "accurate" picture of reality than the former (Goodwin, 1991). In addition to the partial/complete pair, the accident/essence pair commonly appears in scientific discourse: Scientists often argue that previous studies have examined only accidental features of an object or phenomenon, while their own identifies its essence (Schiappa, 1985). In addition to formulae, dissociation can reorganize other facts and observations. Schiappa (1993, 2003), for example, has examined attempts to redefine death, in which some advocates dissociate death into cardiac and brain death, and posit that the latter is the more accurate, realistic definition because human consciousness resides in the brain. Such dissociation reorganizes and revalues facts and physical observations: Absence of brain activity signifies "real" death more accurately than absence of a heartbeat.

The prototypical philosophical pair is appearance/reality (Perelman & Olbrechts-Tyteca, 1958/1969, p. 415), but the meaning of prototypical is open to debate. For Zarefsky (1998), prototypical designates frequency, that is, appearance/reality is a common philosophical pair (p. 8). Many analyses of dissociation do not directly discuss this pair (Murphy, 2004; Walton, 2001; Zarefsky, 1980; Zarefsky et al., 1984), but studies of real definition treat it as the primary element of dissociation (Goodwin, 1991; McGee, 1999; Schiappa, 1985, 1993, 2003). Such apparently conflicting approaches actually represent different points on a continuum of dissociative practices. The practice of real definition can occur unconsciously just as often as consciously and strategically. Approaches to definitional argumentation that take the prototypical nature of appearance/reality to be a description of frequency tend to focus on deliberate, strategic dissociations. Ultimately, however, dissociation can be both: An implicit definition of "reality" often makes subsequent strategic dissociative arguments possible.

The dissociations that occur in real definitions are an essentialist answer to questions of the form, "What is X?" (Schiappa, 1985, 2003). In real definition, "some sort of dissociation is unavoidable. When a novel real definition is put forth, we immediately have competing claims about what some part of the world 'really is'" (Schiappa, 2003, p. 37). Because real definitions implicate essentialism, or naive realism, the appearance/reality pair becomes not simply common but primary: "Every philosophical pair, represented by the general formulation term I/term II, aligns itself with the primary dissociation, the apparent/the real" (Goodwin, 1991, p. 150). Real definitions rely on an essentialist view of language as simply representational: "The persuasiveness of the language of essentialism and dissociation is based upon acceptance of something like a picture theory of language. The definition which captures the 'essence' of an object is one which accurately pictures reality" (Schiappa, 1985, p. 77; emphasis in original). (1) Dissociation usually reproduces problematic ideas about language and reality that limit or exclude nonrepresentational elements such as illocutionary and persuasive acts.

A superior approach begins in a pragmatic theory of definition. McGee's (1999) "constructivist" approach would

distinguish between the contingent essences suggested by the ongoing social practice of definition, what philosophers would call nominal definitions marking how words are used, and the permanent essences that are alleged to inhere objectively in reality and that are purportedly isolated in real definitions. (pp. 153-134; emphasis in original)

Schiappa (2003) also offers several suggestions under the rubric of "pragmatically essentialized" real definitions (pp. 176-177). He advises that scholars be reflexive in language use (Schiappa, 1985, p. 80) and recognize "that definitions are human-made, not found; constructed, not discovered" (Schiappa, 1993, p. 413). Although pragmatism represents an ideal approach to dissociation and definition, extant pragmatic and constructivist approaches leave what they view as the essentialist core--the focus on real or essential characteristics embodied by the appearance/reality pair--intact (albeit bracketed by reflexivity and awareness that definitions are human-made). This essay advances the pragmatic approach through a different view of appearance/reality and real definitions in science that removes the "essentializing" component of pragmatic essentialism.

Goodwin's (1991) distinction between "reality" and "the real" points toward this solution:

[Reality] refers to an onto-philosophic concept tied to the metaphysics of an objective, inherently knowable world order.... [The real], however, refers to a psycho-social concept tied to an epistemology that underscores the power of human perception, cognition, language, and society to shape our understanding of, and our reactions to, the world. (p. 149)

The "real" in the appearance/reality pair should be understood as a psychological and social category created through lived experience. What counts as "the real" differs among different groups and will change over time within a group. It follows, in this approach, that dissociative arguments have different uses in different communities of, say, biologists and politicians. One difference will be which philosophical pairs are used to dissociate. Because philosophical pairs reflect particular normative and epistemic concerns, different pairs may be more or less central to the dissociative practices of specific communities.

Dissociation divides a unitary concept into parts that then form a hierarchical relationship on the basis of a philosophical pair. When dissociation occurs in the process of real definition, the primary philosophical pair is appearance/reality and the real definitions shape one's psycho-social world. Real definitions thus often are implicit and appear as uncontroversial arguments (Goodnight, 1982). Other philosophical pairs are possible, however, including those that uniquely address the epistemic concerns of a specific group. Concerns about essentialism are mitigated when the "reality" of the appearance/reality pair is understood to be a psycho-social consensus about how to use language and organize the world rather than naive realism.


Dissociation shapes the psycho-social consensus that comprises science, a realm of human activity often viewed as the bastion of realism. Dissociations categorize scientists' objects of study and reorganize their conceptual and linguistic tools. Dissociation created conceptual space for research on ES cells, space that was necessitated by efforts to model the earliest stages of mammalian life and broader scientific trends. Scientists linked stem cell to the concept of developmental models. The ideal model would comprise genetically perfect, robust specimens that would facilitate investigation of mammalian, and specifically human, development. As research progressed and more models became available, scientists reshaped conceptual and normative concerns into philosophical pairs that dissociated stem cells, creating a hierarchy of cell types. These dissociations ultimately provide the grounds for contemporary arguments about potential medical applications of stem cell research.

Developmental Models and EC Cells as Stem Cells

Stem cell research occurs at the confluence of multiple streams of investigation. (2) Two of these streams are biological modeling and embryology (study of development from fertilized egg to adult). Further, because it breaches the border between species, stem cell research must account for and negotiate biological differences between mice and humans and differing experimental practices.

Modeling has been a key component of biology since the early twentieth century (Davis, 2003, 2004). A biological model is "an organism that can be taken to represent (that is, stand in for) a class of organisms" (Keller, 2002, p. 115). (3) According to Rowland Davis (2003), modeling depends upon acquisition and integration of information about genetics and the physical and biochemical properties of the model organism or cell type. Developmental modeling is prompted by embryologists' desire better to understand the earliest stages of mammalian development. Unlike other biological modeling, developmental modeling does not require an entire organism. Because the goal is to study how an organism comes to be in the first place, individual cells capable of recapitulating, in whole or in part, the process of growth from fertilized egg to complete organism are sufficient.

This sketch of biological modeling reveals some of the normative and cognitive criteria that can organize and dissociate potential models. Because genetic explanations are considered the most powerful in biology (Ceccarelli, 2001b; Keller, 1995, 2000, 2002), and because models link genetic information to an organism's manifest physical characteristics, a model should be genetically normal, avoiding mutations and other abnormalities whenever possible. Also, because it must recapitulate the earliest stages of life, a developmental model should be derived from the earliest stage that can be isolated and sustained in the laboratory. Finally, a model should reveal how an organism's multitude of tissues and organs develop; it should be sufficiently robust to recapitulate all the branching paths of development--from single cell to heart cell, brain cell, liver cell, etc.

Originally, models of mammalian development were labeled stem cells. Although not explicitly invoked, this phrase immediately suggests an arboreal metaphor, that is, the stem of a tree or other plant, sending out offshoots or branches. Its latent metaphorical power has helped keep the phrase in use for more than 40 years. The first model of early development was embryonic carcinoma (EC) cells, which were isolated from mouse teratocarcinomas--tumors of the testes and ovaries--in the 1960s (Kleinsmith & Pierce, 1964; Martin, 1980). Scientists had known since 1907 that these tumors contained a unique combination of cells from tissues found throughout the body. In 1950, they identified a type of cell that did not belong to any specific organ or tissue (Fawcett, 1950; Fekete & Ferrigno, 1952), which Leroy Stevens (1958, 1959, 1960, 1962) eventually isolated. For more than 20 years, only EC cells from mice were available. Then, in the mid-1980s, a laboratory team led by Peter Andrews successfully isolated EC cells from human teratomas (Andrews et al., 1984). Differences between the two species and the need to adapt lab techniques designed for one species to study of the other account for this time lag (Andrews, 1988).

Dating from the earliest studies, scientists called EC cells stem cells. An early study by Kleinsmith and Pierce (1964) claims, "teratocarcinomas arise by morphogenesis from undifferentiated stem cells" (p. 1544). Gall Martin (1980) notes, "Stem cells can be isolated from teratocarcinomas and cultured in vitro" (p. 769). She links these stem cells specifically to EC cells: "Some stem cells, instead of differentiating, continue to proliferate in the undifferentiated state. They thus form nests of pluripotent embryonal carcinoma cells interspersed in the disorganized mixture of differentiated derivatives" (p. 768). Andrews et al. (1984) report on "the role of embryonal carcinoma (EC) cells as the pluripotent stem cells of the tumors" (p. 147). EC cells are stem cells, found throughout these tumors and equivalent to the cells found in the early embryo.

Scientists also immediately linked EC cells to the concept of developmental models. According to Andrews et al. (1984):

The evident embryonic character of teratocarcinomas has suggested their use as a tool for the investigation of embryonic cellular differentiation.... In murine teratocarcinomas the role of embryonal carcinoma (EC) cells as the pluripotent stem cells of the tumors, as well as their developmental equivalence to normal early embryonic cells, has been extensively documented. (p. 147)

Similarly, Martin (1980) claims that "use of these tumor cells as a model system for the study of mammalian development in vitro circumvents many of the difficulties of working with embryonic material" (p. 768; see also Andrews et al., 1996). Finally, Roach, Cooper, Bennett, and Pera (1993) note, "Cultured cell lines from human teratomas provide models to study molecules which might regulate tumour growth or normal embryonic development" (p. 82).

Thus, scientists identified EC cells as stem cells and associated stem cell with model for development. EC cells helped reveal how a single fertilized egg could multiply and differentiate into the many types of cells in a body. Soon, however, scientists identified a new stem cell that quickly supplanted EC cells: ES cells, which were isolated first in mice (Evans & Kaufman, 1981; Martin, 1981) and then in humans (Thomson et al., 1998). Species differences impacted ES cell research just as they had affected EC cell research: 17 years passed before laboratory methods that enabled isolation and sustenance of mouse ES cells were adapted for application to human ES cells (Schuldiner, Yanuka, Itskovitz-Eldor, Melton, & Benvenisty, 2000). These differences meant that conceptual reorganization, first prompted by the isolation of mouse ES cells, was repeated many years later, when human ES cells were isolated.

Conceptual reorganization was demanded because knowledge of both EC and ES cells raised the question, which cell type was "really" a stem cell? Because stem cells were valued as models for development, the criteria for an adequate model--genetic normalcy, early point of origin, and developmental robustness--could be transformed into the "normative and explanatory" poles of a series of philosophical pairs (Perelman & Olbrechts-Tyteca, 1958/1969, p. 416). Employing three ad hoc pairs, scientists distinguished between embryonic carcinoma cells and embryonic stem cells (a dissociation that also would make subsequent dissociation of embryonic stem cells and embryonic germ cells possible).

Dissociating EC and ES Cells

Published reports show how scientists gradually dissociated ES cells from other cell types. (4) First, scientists acknowledged some similarities between ES and EC cells. Both represent populations of undifferentiated cells, that is, cells that have not yet become specific tissues (Gardner & Beddington, 1988, pp. 13, 20). ES and EC cells also look and behave similarly: "ES cells closely resemble EC cells in morphology, growth behavior, and marker expression" (Smith, 2001, p. 437; see also Thomson & Odorico, 2000). Both produce a chemical, Oct-4, that is considered necessary for maintenance of pluripotent, undifferentiated cells (Nichols, 2001; Smith, 2001). Finally, both can produce teratomas when implanted into mice (Evans & Kaufman, 1981; Martin, 1981).

Embryonic stem and carcinoma cells, which are similar in several respects, initially were understood as belonging to the same category; both belonged to the category stem cells. Yet, ES and EC cells also are different. Eventually, through application of three philosophical pairs--aberrant/normal, secondary/original, and weak/strong--these differences were ordered hierarchically to dissociate stem cell so that it came to refer only to ES cells, while relegating EC cells to an inferior position.

The aberrant/normal pair entered into comparisons of the genomes of EC and ES cells. Most EC cells have additional chromosomes. When they first were isolated in 1981, Evans and Kaufman (1981) found that ES cells, in contrast, had a normal number of chromosomes. As Smith (2001) notes in the technical language of science, "EC cells are almost always aneuploid," while "ES cells maintain a diploid karyotype" (pp. 436-437, 438). Thomson et al. (1995) go further, ordering this difference hierarchically: "All pluripotent human EC cell lines derived to date are aneuploid, suggesting EC cells may not provide a completely accurate representation of normal differentiation" (p. 7844). Hence, stem cell comes to be dissociated as ES cells come to be understood as genetically normal while EC cells are seen as genetically aberrant.

Stem cell is dissociated further via the secondary/original philosophical pair. ES cells are described as originating in a more primal source, the inner cell mass of blastocysts. The blastocyst is one of the earliest stages of embryonic life; it contains the inner cell mass, the group of cells that produces the organism, be it mouse or human (U.S. Department of Health and Human Services, 2006, pp. F-l, F-5). EC cells come from tumors that appear at later stages of development. In announcing the isolation of ES cells in mice, Martin (1981) names them differently in order to emphasize their superior origin: "Such cells were termed embryonic stem cells [emphasis in original] to denote their origin directly from embryos and to distinguish them from embryonal carcinoma cells derived from teratocarcinomas" (p. 7635; see also Thomson et al., 1998, p. 1145). Finally, for Nichols (2001), their different origin is a significant reason why ES cells represent "a very important step towards cell replacement therapy" (p. R505). Hence, stem cell is further dissociated as ES cells are seen to originate directly from embryos at a very early stage of development, while EC cells derive from a secondary source, that is, tumors arising in later stages of development.

Finally, stem cell is dissociated through the philosophical pair weak/strong. Of concern here was a cell's ability to differentiate--to become other types of cells--and thereby contribute to the development of an organism. According to Thomson et al. (1995), EC cells are inferior in this respect: "The range of differentiation obtained from human EC cell lines is more limited than that obtained from mouse ES cells and varies widely between cell lines" (p. 7844). Smith (2001) concurs: "Most EC cell lines show poor differentiation potential in vitro and in vivo and contribute poorly to chimeras and/or produce embryonic tumors" (p. 436). Others emphasize the comparative superiority of ES cells: "Similar to their mouse counterparts, human ES cell lines have both more advanced and more consistent developmental potential compared with human EC cell lines" (Thomson & Odorico, 2000, p. 54). In this way, ES and EC cells are distinguished further: the latter are weaker--less able to differentiate, less potent--than the former.

These three ad hoc pairs--aberrant/normal, secondary/original and weak/strong--in combination enact the primordial philosophical pair, apparent/real. That is, they dissociate stem cell into cells that "appear" to be stem cells (EC cells) and cells that "really" are stem cells (ES cells). Revealingly, after noting the limited differentiation potential, abnormal karyotype and origin of EC cells, Smith (2001) says, "Studies with EC cells did eventually pave the way for the establishment of 'true' embryo stem cell cultures" (p. 437). The dissociative argument here is that embryonic carcinoma cells are not really stem cells. This argument first occurred when mouse ES cells were isolated. When repeated with human ES cells, the cognitive workload of dissociation is reduced; the earlier dissociation of mouse cell types makes the conceptual reorganization easier.

In sum, a pragmatic search for the most effective models of development led biologists to redefine stem cell. This redefinition was achieved through dissociation according to three philosophical pairs: Only ES cells, possessing a normal karyotype, primacy of origin, and greater differentiation potential, deserve the title. This dissociation also reveals that the appearance/reality pair reflects a psycho-social consensus about how words are used and objects are categorized: in this case, an agreement that stem cell will refer to objects that possess a specific origin, power, and karyotype.

ES Cells and EG Cells: A Potential Dissociation

In addition to embryonic carcinoma and embryonic stem cells, researchers also have isolated embryonic germ (EG) cells. These cells are derived from primordial germ cells, the cells that ultimately produce sperm or eggs and are obtained from 5- to 9-week-old embryos (Shamblott et al., 1998). Like ES cells, EG cells have been identified as a model of development and a platform for biomedical projects. Some researchers dissociate the two through the aberrant/normal and weak/strong pairs, but others doubt that their differences are substantial. Currently, dissociation is largely a potential strategy that might be realized fully in the future, or not.

Researchers note that EG and ES cells are similar in several respects. Both types express Oct-4, have a normal karyotype, and possess similar powers of differentiation (Nichols, 2001; Smith, 2001; Thomson & Odorico, 2000). "In most respects," Smith (2001) notes, EG cells "are indistinguishable from blastocyst-derived ES cells" (p. 440). Downplaying differing origins and positing equal potency, Watt and Hogan (2000) call both stem cells: "pluripotent stem cells can be cultured from aborted human fetuses or from spare embryos from in vitro fertilization procedures" (p. 1427). Thomson and Odorico (2000) equate their potentials as developmental models: "Human ES and EG cells provide an exciting new model for understanding the differentiation and function of human tissue, offer new strategies for drug discovery and testing, and promise new therapies" (p. 53). Some researchers even suggest that EG and ES cells have the same morphology, or appearance (Smith, 2001; Tada et al., 1998), although others assert that this is true only in mice, not humans (Nichols, 2001; Thomson & Odorico, 2000).

Researchers do agree that EG cells differ from ES cells in their capacity to erase genetic imprints (Tada, Tada, Lefebvre, Barton, & Surani, 1997; Tada, Takahama, Abe, Nakatsuji, & Tada, 2001; Tada et al., 1998). For some, this capacity of EG cells does not compromise their developmental potential: They still possess the same capacity for differentiation as ES cells do (Tada et al., 2001). Others, however, claim that erasure of the imprint "compromises the developmental potential of EG cells derived from later stage PGCs" (Smith, 2001, p. 440). Thus, in comparison with ES cells, the developmental potency of at least some EG cells is suspect.

This ambivalence, or difference of opinion, about cell morphology and developmental potential probably explains why the dissociation of EG cells and ES cells has not been completed. Thomson and Odorico (2000) argue:

It is not yet clear whether the apparent morphological and phenotypical differences between human ES and EG cells reflect basic biological differences resulting from their different origins, or merely reflect the different culture conditions used to isolate and propagate these two cell types. (p. 54)

But future dissociation remains possible. Existing research has prepared the ground for dissociation based either on aberrant/normal--imprint loss affects only aberrant (EG) cells, not normal (ES) cells--or on weak/strong--imprint loss weakens EG cells' potential for differentiation and development in comparison to ES cells. As of 2005, research had not identified any differences between ES and EG cells that would require complete dissociation of the two cell types (Western & Surani, 2002; Wobus & Boheler, 2005); future experimentation may determine whether stem cell yet will be dissociated even further.

Providing Grounds for Future Argument

Scientists have employed dissociative arguments in debates concerning which of various stem-like cells represents the best model for biological development. These dissociative definitions of stem cell utilized philosophical pairs that reflected a pragmatic interest in models of mammalian development. As stem cell was redefined, however, the values encoded into the second term in each pair--normal, original and strong--became the virtues of "real" stem cells. These values, however, are multifunctional: They can be deployed in multiple kinds of arguments about stem cells, not just arguments about models for development. The philosophical pairs used in real definitions of stem cell also have been transformed into the grounds for conscious, strategic scientific and political arguments about ES cells (Murphy, 2004; Stahl, 2002).

The weak/strong pair rather easily became the extremes of a hierarchy of potency that figures in subsequent scientific and political arguments about embryonic and adult stem cells. Gage (2000) best illustrates this hierarchy in scientific arguments. He posits a hierarchy with absolute strength--called totipotency and represented by the fertilized egg--at one end and absolute weakness--the totally differentiated cells of the developed organism--at the other. "Pluripotent" embryonic stem cells are more powerful than "multipotent" adult stem cells. Testifying before a U.S. Senate committee in 2000, one scientist noted that embryonic stem cells "have truly amazing abilities to self-renew and to form many different cell types, even complex tissues, but in contrast, the full potential of adult stem cells is uncertain, and, in fact, there is evidence to suggest they may be more limited" (Stem Cell Research, Part 3, 2000). This ranking of embryonic and adult stem cells becomes a basis upon which nonscientists then argue for government support for embryonic stem cell research. At a subsequent hearing, actor Christopher Reeve claimed, "If the government forces scientists to attempt to make adult stem cells behave like embryonic stem cells, they might waste five years or more and fail. In the meantime, hundreds of thousands will have died" (Dangers of Cloning, 2002). In short, the weak/strong pair, which first appeared in real definitions dissociating ES and EC cells, became the basis for a hierarchy of potency that enabled political arguments that, being more powerful, ES cells are more likely to produce therapies for a variety of conditions.

Similarly, the aberrant/normal pair shapes discussion of the quality of the stem cell lines that are eligible for federal funding. The 5-year-old groups of ES cells eligible for funding develop chromosomal abnormalities under certain laboratory conditions, which degrades their potential uses in medical therapies (Draper et al., 2004; Mitalipova et al., 2005; Pera, 2004). This fact has entered public argumentation over stem cell research. In an interview in The New York Times, researcher Douglas Melton calls the eligible lines "problematic": "Some had abnormal chromosomes, like a cancer cell might. If you're using stem cells to create pancreatic beta or muscle or nerve cells, you want to begin with high-quality normal cells." (Dreifus, 2006, [paragraph] 36). In this way, "abnormalities" in the restricted cell lines eligible for federal research support become part of the argument for easing or lifting these restrictions.

The secondary/original pair figures in arguments opposed to, rather than in favor of, stem cell research, and more subtly so. Because ES cells originate in the human embryo, research is viewed by opponents as murder of developing life. At the very first Congressional hearing on stem cells, in 1998, a representative of the National Conference of Catholic Bishops argued that isolating ES cells was comparable to ripping out a person's internal organs: "The effect is the same as if one were to 'isolate' the heart and lungs from an adult human" (Stem Cell Research, 1998, testimony of Richard M. Doerflinger). In a speech on stem cell research and adoption of frozen embryos in 2005, President Bush said:

In the complex debate over embryonic stem cell research, we must remember that real human lives are involved--both the lives of those with diseases that might find cures from this research, and the lives of the embryos that will be destroyed in the process. ([paragraph] 3)

Such arguments, of course, presume that embryonic life is equivalent to human life. Although this belief clearly derives from prior, long-standing opposition to abortion, it also is reinforced by previous scientific claims about ES cells' origin (and potency). As a result, proponents of ES cell research face a complicated task: arguing for the value of embryos without strengthening counter-arguments based on their right to life.


Dissociations, which can range from implicit and unconscious to explicit and conscious, reorganize and restructure concepts (Schiappa, 1985). When used in real definitions, they reshape our worldview; if, implicit, this reorganization of our psycho-social consensus about "reality" takes the form of uncontroversial arguments (Goodnight, 1982). This study suggests four conclusions about dissociative arguments.

First, this study reveals how dissociation can occur with some, but minimal, conscious effort. Although clearly not unconscious, dissociations of stem cell required less effort, and were less strategic, than did Ronald Reagan's redefinition of needy. Thus, study of its uses in the scientific context broadens our understanding of dissociative argumentation, revealing a continuum along which uncontroversial real definitions also can become the grounds for strategic political dissociations.

Second, this analysis refines our understanding of real definitions and suggests a way to resolve concerns about essentialism. Some have argued that dissociative real definitions naively presume to assert something about "reality." Most solutions have involved some form of "pragmatic essentializing," in which this assertion, although unavoidable, is bracketed by a reflexive understanding of definition and language. This study shows that the "real" in real definitions can be understood as the psycho-social consensus among a group of language users. Indeed, the language users studied here--scientists (quite possibly the epitome of realists)--grounded their real definitions of stern cell in a consensus about the values and needs of a specific research program. Examination of scientific or public dissociations does not require naive realist assumptions. Claims of naive realism should be based on a reading of the rhetorical moves accompanying any dissociative argument, not on dissociation's mere presence alone.

Third, dissociative real definitions have profound material consequences. By redefining and reorganizing the objects vying to be models of development in the laboratory--ES, EC and EG cells--dissociation also led to a reorganization of the social elements of science. For one thing, scientists studying mammalian and human development had to retrain themselves to the methods associated with the mouse and human ES cells; new practices and equipment for isolating and growing these cells had to be developed (Andrews, 1998; Jones & Thomson, 2000; Schuldiner et al., 2000). For another, the economic relationship among laboratories was reorganized: New labs became the source for basic research materials and the holders of new patents. In 1984, researchers studying human "stem cells" (i.e., human EC cells) relied on Peter Andrews' lab for the best-studied line, Tera-2 (Andrews et al., 1984; Jones & Thomson, 2000; Thompson et al., 1984). In 1998, the University of Wisconsin, where human ES cells were discovered, patented the processes for isolating them. The university is a major supplier of ES cells ("NIH Human Embryonic Stem Cell Registry," 2006); its patents enable it to profit from all research on, and all attempts to supply, embryonic stem cells in the United States and, possibly, the world (Stem Cells, 2001, 2001; Stem Cell Research, 1998; U.S. Department of Health and Human Services, 2006).

Finally, this study helps us see how rhetoric reshapes science. This is not to suggest, as Gross (1990) argues, that science is merely a subspecies of rhetorical practice. Rather, like Shapin and Schaffer (1985), I see the rhetorical, material, and social playing theoretically equal roles while, in this specific case, the power of rhetoric comes to the fore. (5) In addition to reorganizing the possible models of mammalian development, real definitions of stem cell became the basis for later, strategic dissociations. Although this might be seen as yet another encroachment by the technical sphere on the besieged bailiwick of the public, I see the interaction among scientific and public concerns in a more constructive light. The issues that arose in scientific and technical discussions of stem cells are congruent with public concerns about biomedical technology. Also, some scientists have identified broadly public motivations for their technical endeavors. Douglas Melton has said that his son's diabetes drives his research into ES cells (Dreifus, 2006), and James Thomson has expressed hope that his isolation of ES cells will contribute to treatments for muscular sclerosis and Downs Syndrome (Thomson et al., 1998). Although a full discussion is not possible here, scholars would do well to consider again the pivotal role of rhetoric in shaping science, and the manner in which rhetoric in science, in turn, is shaped by the demands placed on scientists by the public's own rhetoric about science.


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(1) Throughout, expressions that are italicized in the original source are noted as such; all others have been added for emphasis.

(2) In addition to the isolation of embryonic stem cells, studies of bone marrow and the body's production of blood led to the identification of blood-forming adult stem cells. These events occurred simultaneously, yet separately. Brief histories of the developments leading to adult stem cell studies are available in Weissman (2000), Weissman, Anderson and Gage (2001), and Wulf, Jackson, and Goodell (2001).

(3) Biological models differ from the mathematical models of physics. According to Keller (2002), model organisms differ from theoretical models because they play different roles in explanation and because biologists and physicists value theoretical models differently. Mathematical models are fictional, abstract entities that may not correspond to any "real" object; yet, they identify qualities that interest physicists, enable predictions about the phenomena represented in the model, and guide further research.

(4) This study is part of a larger project; for present purposes a sample of scientific writing was developed by, first, collecting the research articles most often cited in review articles about stem cell research and, second, gathering those articles most often cited in these research articles.

(5) For more on the role of rhetoric in the formation of scientific knowledge, see Ceccarelli (2001a) and Gross and Keith (1997).

John Lynch, Department of Communication, University of Cincinnati. This essay is derived from the author's dissertation at the University of Georgia, directed by Celeste Condit. An earlier version of this essay was presented at the National Communication Association convention, Boston, MA, November, 2005. The author would like to thank the editor and reviewers for their helpful comments. Correspondence concerning this article should be addressed to John Lynch, Department of Communication, University of Cincinnati, P.O. Box 210184, Cincinnati, Ohio 45220-0184. E-mail:
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