The Janus-Face of Philosophy of Biology

PATRICIA WILLIAMS

Department of Philosophy and ReligionHollins CollegeRoanoke, Virginia 24020, U.S.A.

A Review of Mohan Matthen and Bernard Linsky (eds.), Philosophy &Biology, Canadian Journal of Philosophy Supplementary Volume 14,University of Calgary Press, 1988, x + 267 pp. $12.00 (paper).

Philosophy of biology, unlike philosophy of physics and philosophy ofscience generally, is Janus-faced. Like philosophy of physics, it looks atlogical and conceptual issues in its chosen discipline. And like philosophyof science generally, it investigates scientific methodology and logic.However, it also uses its chosen discipline to scrutinize philosophicalissues. This comes about because biology seems to have something to tellus about human nature, and philosophical theories frequently depend onsome concept of human nature. Both of these faces of philosophy ofbiology are represented in this collection of essays, essays which areprinted here for the first time.

More is represented here as well, for two biologists contribute to thevolume, one speaking directly to philosophers about the relevance of theirdiscipline to his and of how that relevance can be increased. This is acomplex, interesting collection, written for professionals in the fields ofboth biology and philosophy. The volume does not have a single focus,and if the reader comes away with a single impression, it is that philosophyof biology is extremely varied and complex.

The volume comes with an informative introduction. I will not repeatwhat is said there, but instead will note the problem each essay addressesas well as each essay's conclusion, then make critical comments whereappropriate. The collection can be divided into two parts, coincident withthe Janus faces of philosophy of biology. I will move from the essays onhuman nature to those dealing with logical and conceptual issues inbiology. But first, one correction to the introduction.

The discussion of Immanuel Kant and Peter Singer on pages 11- 12 isnot accurate. Kant does not abstract away from our desires in his ethics,although Singer does; Kant eschews desires, even benevolent ones, as abasis for ethics (Kant 1964, pp. 66-67). Singer (1981, pp. 3-53) holdsthat reason operates on our evolved, altruistic motives, not on our evolvedselfish ones, to yield a universal morality. The problem of ethics, as he

Biology and Philosophy 6: 351-361, 1991.© 1991 KluwerAcademic Publishers. Printed in the Netherlands.

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sees it, is how to universalize our evolved altruism to a circle wider thanthat of altruism toward kin and clan with which kin selection has alreadyprovided us.

The collection contains three essays concerned with evolutionarybiology and human nature. Two, those by Michael Ruse and Elliott Sober,discuss our ethical dispositions. The third, by Paul Thompson, addressesepistemology. I include Thomas Wegmann's essay in this group because ofits relationship to Thompson's article.

Ruse's essay is entitled, "Evolutionary Ethics: Healthy Prospect or LastInfirmity?" Much philosophical confusion would be avoided were he tofollow the lead of Neil Tennant (1983) and refer to his version of ethics as"evolved", not "evolutionary". The problem he addresses concerns theevolution of our ethical dispositions and the effect that our knowledge oftheir natural origin might have on attempts to justify ethics. He is notconcerned, as the old evolutionary ethics was, with deriving an ethicaltheory from the direction of evolution or the theory of natural selection.Evolutionary ethics clearly commits the naturalistic fallacy; Ruse's positiondoes not. Ruse's conclusion is complex. He seems to hold that three kindsof ethical dispositions evolved: particular normative values, a more generaltendency to view actions and motives as right or wrong, and a belief in"disinterested" or "objective" morality. He thinks the natural origin of ourethical dispositions leaves us with no possibility of a philosophical justifi-cation for ethics.

There is much that needs reconsideration and clarification in Ruse'stheory, but his theory is the best we currently have in evolved ethics, andthere is much in it that is worth careful attention by philosophers. Thecentral part of his essay addresses the question, by what means has ourevolution enabled human beings to cooperate so well? He suggests threepossibilities. The first is genetic determinism, as in the ants. They cooperatebecause they cannot do otherwise. Ruse dismisses this possibility for usbecause we produce few offspring, and organisms which produce fewoffspring and invest heavily in parental care cannot afford the numerouslosses of offspring that rigidly determined behavior would entail (p. 35).The second is full, rational calculation of our own self-interest, calculationwhich would often lead to cooperation with others for the individual's ownwelfare. He rejects this possibility because of biological difficulties andbecause we frequently need to act too quickly to do the calculations (pp.35-36). The third is the evolution of morality (p. 36).

Ruse thinks that morality consists primarily of belief in objective values.It is this belief that he terms "genuine altruism" (p. 36) as opposed to the"altruism" of the biologists, which simply refers to cooperative behavioramong other animals, which, as far as I can ascertain, Ruse thinks isgenetically determined, as in the ants. This altruism (without quotationmarks) is an emotion, a sentiment, a feeling, that we ought to cooperate.

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And Ruse thinks that, without our evolved tendency to believe our valuesto be objective, we would give in to our natural, selfish desires, ". . . thenin a few generations the moral beings will have been wiped out by theselfish" (p. 42).

Once the heart of Ruse's position is laid bare like this, it is not difficultto see that something is wrong with it. Under this evolutionary scenario,how is he going to explain the existence of cooperative behavior amongour very close evolutionary relatives, the other primates? The sameevolutionary causes which shaped cooperation in them shaped it in us, andRuse's reasons for rejecting genetic determinism and pure calculation in usapply equally well to them. Yet, Ruse does not intend to suggest that otherprimates are moral beings in the sense that people are.

The crucial step which Ruse has missed was argued for by CharlesDarwin more than a century ago in The Descent of Man (1981, pp. 74-84). We, like the chimpanzees, are social beings, and our evolutionaryancestors were social beings, cooperating with each other long before weevolved from them into moral beings. To explain the evolution of socialcooperation in the primates and in us requires a fourth possibility. I willnot argue for it here, but the most likely possibility appears to be DavidHume's (1948, pp. 270-275): we have been endowed with a naturalsentiment of benevolence. Even without a belief in objective values, wewould show concern for the welfare of others (the original meaning of theterm "altruism"). Due to the power of kin selection, we would show itespecially for our closest relatives. This possibility implies that, contrary toRuse's assumption, we are not totally selfish creatures apart from ourfeelings that objective morality commands us to behave cooperatively.Rather, we evolved natural, social dispositions.

In any case, this central part of Ruse's argument needs reworking. Hisother main argument, which would not be undermined by altering histheory in the direction I have suggested, is that knowledge of the naturalorigin of our normative ethics leaves us without justification for them. Hefirst argues that "morality has no ultimate ontological significance" (p. 42),then argues against the "middle position" (pp. 62-63) of Kant, that,although morality does not have ontological status, yet "morality is insome sense a set of necessary conditions which is binding on rationalbeings" (p. 63). There is some confusion in Ruse's discussion of theKantian position; nonetheless, I would like to suggest that evolved ethicsdoes offer a serious challenge to ethical rationalism, and that the reverse isalso true.

The challenge of evolved ethics to ethical rationalism is one which Ruserecognizes. Even supposing, what Ruse does not accept, that reason candevise imperatives which are logically binding on all rational creatures onpain of self-contradiction, what if we have evolved in such a manner as tobe unable to follow those imperatives consistently? Ruse thinks this would

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make them, or any other type of objective morality which ran against acentral grain of human nature, "irrelevant to human life" (p. 62). I am lesssanguine. I think we would have acquired knowledge of a central humantragedy, or, if one were to phrase it theologically, knowledge of originalsin. That is, we would know what we ought to do, yet we would also knowthat we have evolved in such a manner as to be unable consistently to doit. We would have to recognize ourselves as inherently flawed ethicalbeings. Beyond giving us such tragic knowledge, however, rationalism'simperatives for human behavior would appear futile, and ethical rational-ism would be reduced to a mere exercise in logic.

Ethical rationalism poses two challenges for evolved ethics. First, itmight justify ethical action which is different from those actions ourevolved ethical sentiments dispose us to do. If so, it can ask Ruse why weshould do what we have evolved to do instead of doing what is ethicallyjustified rationally. In another work, Ruse has responded to that query:doing what we have not evolved to do is difficult, and may cause socialand/or psychological stress (Ruse and Wilson 1986). This answer, how-ever, sags under the psychological phenomenon that human beings need,and even seek, challenges, sometimes very stressful ones, and that ethicalchallenges are among those we seek.

Secondly, it might justify ethical action which is very similar to thoseactions which our evolved ethical sentiments dispose us to do. If so, then aunified theory is possible in ethics, one based on the conjunction of ourevolved dispositions with our evolved capacity to deduce a rational justi-fication for ethics. I am currently attempting to develop such a unifiedtheory.

Thus, Ruse's theory, which is founded on the well-accepted biologicaltheories of individual and kin selection, raises some interesting philoso-phical questions and challenges.

Sober asks "What Is Evolutionary Altruism?" In contrast to Ruse, herests his answer completely on group selection. He offers a clear anduseful discussion of the differences between our vernacular use of theterm, "altruism," and biologists' technical use of the term, if they are groupselectionists. He also gives a lucid exposition of group selection, fromwhich he thinks our human altruism derives, if we have it. His focus is on"what altruism is, not whether it exists" (p. 97). "Vernacular altruism" isessentially psychological, but not essentially reproductive or comparative;if derived from group selection, biologists' technical "altruism" is theopposite (p. 79).

Sober's essay is to be faulted more for what it passes over than for whatit says. Sober fails to give an adequate discussion of kin selection, men-tioning it only in a footnote (p. 93). Yet, almost all biologists working insociobiology look to kin relationships, not to group selection in Sober'ssense, as the primary source for "altruism"; indeed, few think that group

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selection in Sober's sense exists in nature, and even "group selectionists"like E. O. Wilson think it rare (1975, pp. 114-115). In addition, thosephilosophers working in evolved ethics consider kin selection an impor-tant source of human altruism - Ruse (1986); Singer (1981); RobertRichards (1987, Appendix 2), myself. If Sober is adequately to addresswhat "altruism" is in biology, then he needs either to include kin selectionin his discussion or to make a strong argument against kin selection asbeing a source of altruism.

Sober's treatment (p. 95) of Darwin's Descent of Man also slights kinselection as a source of human altruism. While it is true that Darwindepends to some extent on group selection as a source for humanaltruism, he employs what we would now call "kin selection" (1981, pp.74-84), too, and kin selection is one of the pillars of his argument forevolution by natural selection in The Origin of Species (1964, pp. 235-244; see Richards 1987, pp. 142-152, for a discussion).

Thompson's "Conceptual and Logical Aspects of the 'New' Evolu-tionary Epistemology" is an important contribution both to epistemologyand to philosophy of science. The "new evolutionary epistemology", likethe new evolved ethics, deals with what may be "literally a product ofDarwinian evolution" (p. 235), not with the old, but still very lively,analogical approaches employed in recent works by Richards (1987) andDavid Hull (1988). Possibly, Thompson should call his version "evolvedepistemology".

The problem he addresses is how to get a sufficiently rich evolutionaryepistemology from which to explore the nature and acquisition of humanknowledge. His answer is to employ "a number of different theoreticalframeworks in an interactive way" (p. 237), especially, but not exclusively,three, "the theory of evolution, a theory of cultural transmission ofknowledge, and a theory of cognition" (p. 243). In order to employ suchdifferent theoretical frameworks, what is required is an alteration ofphilosophy of science from the old, logical positivist, syntactic view to thenew, semantic view. Thompson discusses each view clearly. More detaileddiscussion of both views may be found in his (1983) which is very lucid,and in Ronald Giere's clear and informative Explaining Science (1988) aswell as in other works which Thompson helpfully lists in his text.

It is part of the semantic view to emphasize technology, which Giererefers to as "embodied knowledge" (1988, p. 140). Wegmann has a verynice article in this collection, "Technology: The Driving Engine of CurrentBiological Advance" which concludes that much of modern biology isdriven by technology, not by theory. As an introduction, he gives a shortbut devastating discussion of Karl Popper (p. 256) and points out that themost cited paper in modem biology is "a method for assaying protein" (p.258). The body of the essay presents three examples from contemporarybiology of major technologically driven discoveries. This essay should be

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required reading in introductory philosophy of science courses as well asin not a few graduate courses.

The volume contains four articles on logical and conceptual issues inbiology, and all of them involve discussions of biological hierarchies, aclear indication f the importance of theories of hierarchy in currentphilosophy of biology. W. Ford Doolittle writes about "HierarchicalApproaches to Genome Evolution", asking especially what contemporarymolecular biology may tell us about the coupling between genotype andphenotype. He concludes that there are biological hierarchies which areboth selected and sorted, and that the selection and sorting at one levelinfluence selection and sorting at other levels.

John Collier's contribution, "Supervenience and Reduction in BiologicalHierarchies" begins the development of what may turn out to be a usefulconcept, "cohesion". "A system," he says, "is cohesive if there are causalinteractions among its parts which make it insensitive to fluctuations in theproperties of its lower level components" (p. 210). He employs theconcept to argue against ontological reductionism in biology. The first partof his essay suffers from over-reliance on technical terms and unduedependence on positivist philosophy of science even where that philoso-phy has been devastatingly criticized.

Edwin Levy discusses "Networks and Teleology". The problem headdresses is whether there is sufficient analogy between the immunesystem (IS-Net) and the neural network (N-Net) for us to consider theIS-Net as well as the N-Net teleological. His conclusion that there issufficient analogy is flawed by two problems to which he himself drawsattention. One is that we do not know enough about the N-Net to make aclose enough analogy to answer the question. But even if we did and couldalso make the analogy work, we would not be able to use it to close thegap Levy wants to close between teleological systems in the sense ofconscious, purposive human behavior and teleological systems employinggoal-seeking like that of non-verbal animals or of artifacts dependent onfeed-back. The analogy will not close this gap because, in order to close it,Levy needs to be able to tell a story for the connection between brain(N-Net) and mind (conscious, purposive human behavior) which we donot have, even in reasonable prospect.

Rosenberg's article is entitled, "Is the Theory of Natural Selection aStatistical Theory?" However, the problem he actually addresses is not asclear as his title suggests. For example, although his title mentions thetheory of natural selection, the concluding subtitle of his essay does not;instead, it adverts to the theory of evolution. His fully stated conclusion isconfusing. He concludes that, when drift is added to the theory of naturalselection, the result is an instrumentalist theory. His reason for thetheory's being instrumentalist is that it is statistical. On the other hand, heconcludes, evolution itself is causally deterministic. This contrast, heproposes, between evolution and the theory of natural selection makes the

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theory of natural selection a very different theory from other scientifictheories.

Rosenberg's conclusion is confusing because Rosenberg conflates severalseparate questions in the course of his article. I will comment upon two:first the relationship between the theories of evolution and natural selec-tion, secondly the relationship between drift and unpredictability in thetheory of evolution.

As far as I can understand what Rosenberg has done, he seems to havereversed the relationship between the theories of evolution and naturalselection. Partly, he reverses them by making the theory of natural selec-tion more comprehensive than the theory of evolution. But it is not.Generally speaking, "evolution" is a very broad term. As any English-language dictionary will indicate, it refers to changes in a system, andalthough it has connotations of orderly change, directional change is notentailed. In biology, what is wanted is a comprehensive theory which willdeal adequately with the diversity and the discontinuity of life which weobserve on Earth (Dobzhansky 1982, pp. 3-14). Currently, the neo-Darwinian theory of evolution is thought to be our best such theory. In thetheory of evolution, "evolution" is a broad term, referring to changes inbiological diversity and discontinuity whether those changes are directionalor not. In contrast, Rosenberg claims that the theory of evolution dealsonly with directional change (p. 199). Directional change, however, is whatthe theory of natural selection deals with, the direction of change beingtoward the adaptation of organisms to their local environments.

The theory of natural selection is a part of the theory of evolution. It isa theory about one mechanism producing the diversity and discontinuitywe see, one mechanism that drives evolution. However, natural selectionmay not be the only evolutionary mechanism, as Rosenberg would have itwhen he equates evolution only with change which is adaptive (p. 199).Darwin (1964) posited other, non-adaptive, evolutionary mechanisms, forexample, sexual selection. Biologists today posit both sexual selection andgenetic drift as mechanisms of evolution; neither is necessarily adaptive.

Rosenberg says drift is not an evolutionary mechanism, yet he doesthink drift is a mechanism of change (p. 199). But, if it is a mechanism forchange, then it is a mechanism for evolution. At the end of the article, hetries to make drift part of the theory of natural selection (p. 206).However, it is not part of that theory because natural selection adaptsorganisms to their local environments, whereas drift does not, except,perhaps, accidentally. Rosenberg cites drift's non-adaptive character as thereason for its not being a part of the theory of evolution (p. 199). But it ispart of the theory of evolution, as is natural selection. Drift is a non-adaptive evolutionary mechanism, whereas natural selection is an adaptiveevolutionary mechanism. Rosenberg has reversed the theories of evolutionand natural selection.

In the process of doing so, he has confused the discussion by Sober

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(1984, pp. 103-134) on chance, a discussion which is, on the whole,quite clear and useful. Sober is not "ambivalent" about the role of drift, asRosenberg says (p. 199); rather, Sober is quite specific that drift is a partof the theory of evolution, a part which makes some accurate predictionsdifficult, namely, predictions based solely on mutation and selection(Sober 1984, p. 110). Rosenberg misquotes Sober. Where Sober says, "Ifdrift is an evolutionary force ... " (p. 117), Rosenberg has "If drift is aselective force .. ." (p. 199). Sober is quite clear that drift is not a selectiveforce, in the sense of natural selection.

The simplest way to clarify Rosenberg's confusion of natural selectionwith evolution while reading his article is to substitute "evolution" for"natural selection" up until the concluding section, then, in addition, tosubstitute "natural selection" for "evolution".

Secondly, I want to comment upon Rosenberg's discussion of unpre-dictability and drift in the theory of evolution. To do so, I must makesome preliminary remarks. Both the theory of natural selection and thetheory of evolution are statistical theories. They are statistical theoriesbecause the discipline of statistics deals with the behavior of aggregateentities (sets or populations) rather than with single entities, and both thetheories of natural selection and of evolution deal with populations oforganisms rather than with single organisms. As Ernst Mayr has empha-sized (1963, pp. 5-6; 1982, pp. 487-488), Darwin introduced populationthinking into biology when he introduced the theories of evolution andnatural selection into it. Unfortunately, Rosenberg confuses the issue byclaiming that the theory of natural selection (as well as the second law ofthermodynamics) is statistical because it makes a claim about the long-runbehavior of systems (p. 187). It is not statistical for this reason. However,it does predict more accurately when it deals with large numbers ofinteractions, as opposed to causal theories which can predict accuratelyonly when dealing with a few interactions.

In fact, the question biologists and philosophers of biology are usuallyasking when they ask whether the theory of evolution is a statistical theoryis, what sort of predictions can it make? Philosophers of biology havebeen concerned with this question because the logical positivists accusethe theory of evolution of being unscientific partly on the grounds thatit cannot predict very much. Philosophers of biology have repeatedlyaddressed this issue. David Hull (1973, pp. 16-36) has a discussion of itshistory.

The clearest way to address the question of the statistical character ofthe theory of evolution and why evolutionary outcomes are difficult topredict is through an understanding of the nature of statistical laws andthe inherent uncertainty of statistical predictions generally, whether theyare about biological evolution or not. Uncertainty arises within statisticaltheories for three reasons. First, statistics deals with aggregates, predicting

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the behavior of the aggregate, not of its individual, constituent parts.Statistical theories do not address the behavior of constituent parts, andthus the behavior of these parts is uncertain under these theories. Thisdoes not mean, however, that the behavior of the individual constituentscannot be predicted, and it certainly does not imply a causality in theinteractions of the parts. There can be causal, deterministic laws at themicro-level, yet statistical laws at the macro-level, as is the case in thermo-dynamics.

Secondly, statistical predictions predict within a range of accuracyrather than predicting exactly, so that there is uncertainty connected withthe predictions themselves. Thirdly, there is always the possibility that theconstituents of the system will fail to interact randomly. Because theconstituent parts must interact randomly in order for ordinary statisticalpredictions to be accurate, non-random interactions will result in inaccur-ate predictions. The constituent parts of the system can fail to interact atrandom for at least two different reasons. The system may be too small toobey the law of large numbers as required by most statistical predictions,or its constituent parts may collude, as they do in James Clerk Maxwell'sdramatization of why the second law of thermodynamics may be over-turned (1875, pp. 328-329) by "Maxwell's demon". In either case, theconstituent parts do not interact with sufficient randomness for accuratestatistical prediction to be possible.

As far as I can ascertain from Rosenberg's discussion, his concernseems to be with unpredictability in the theory of evolution (not naturalselection), and because this is his concern, he focuses on drift, for, ashe comments, "evolutionary biologists seem to identify the source ofunpredictability in evolution with the phenomenon of drift" (p. 190).Rosenberg gives a clear discussion of drift, emphasizing its increasingrelevance as population size decreases (pp. 190-193), but later, in aconfused example about imaginary giraffes (pp. 195-197), he conflatesdrift with natural selection so that there is no hope of learning from hisdiscussion what the role of drift in the theory of evolution might be.

My understanding is that its role is to decrease randomness in evolutionbecause it occurs in populations too small to obey the law of largenumbers. In doing so, it increases unpredictability. It is one example ofhow the constituent parts of a biological system may fail to interact withsufficient randomness that the behavior of the system is predictable. Theconstituent parts of a biological system may behave non-randomly forother reasons as well. The constituent parts (organisms) may collude. Intheir sexual interactions, organisms frequently do collude due to the factthat they do not necessarily mate at random. Instead, they select eachother. Sexual selection, too, decreases the randomness of the system,thereby increasing unpredictability.

In his contribution to this volume, then, Rosenberg makes at least two

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errors. The first is that he reverses the relationship between the theories ofevolution and natural selection. In the process, he displaces drift from itsrole in the theory of evolution and, instead, attempts to understand it aspart of the theory of natural selection. It seems partly to be this displace-ment which leads him to become confused about the relationship betweenstatistics and unpredictability in the theory of evolution. The theory ofevolution is a statistical theory, but statistical theories do not inherentlylack predictive power. However, when drift is included in the theory ofevolution, it makes prediction difficult by ordinary statistical meansbecause it introduces non-randomizing factors into the theory.

The volume also contains one historical article, that by R. J. Hankinson,"Galen Explains the Elephant". The article, which is clear and interesting,is concerned with the connection between Galen's extremely Panglossianteleology and his anatomical researches. The author concludes that Galenwas a careful and systematic scientist working within the framework whichit was most rational to adopt at the time.

The volume under discussion, then, is a complex work. The articles itcontains are interesting, informative, and provocative, if somewhat unevenin quality. The collection includes essays which represent the Janus-facesof the philosophy of biology, and this comprehensive representation is oneof its assets.

REFERENCES

Darwin, C.: 1964, On the Origin of Species, Harvard University Press, Cambridge, Mass.Darwin, C.: 1981, The Descent of Man, and Selection in Relation to Sex, Princeton

University Press, Princeton, N.J.Dobzhansky, Th.: 1982, Genetics and the Origin of Species, Columbia University Press,

New York.Giere, R. N.: 1988, Explaining Science: A Cognitive Approach, University of Chicago

Press, Chicago.Hull, D. L.: 1973, Darwin and His Critics: The Reception of Darwin's Theory of Evolution

by the Scientific Community, University of Chicago Press, Chicago.Hull, D. L.: 1988, Science as a Process: An Evolutionary Account of the Social and

Conceptual Development of Science, University of Chicago Press, Chicago.Hume, D.: 1948, Hume's Moral and Political Philosophy, Hafner Press, New York.Kant, I.: 1964, Groundwork of the Metaphysic of Morals (tr.: H. J. Paton), Harper Torch-

books, New York.Maxwell, J. C.: 1875, Theory of Heat, D. Appleton and Co., New York.Mayr, E.: 1963, Animal Species and Evolution, Belknap Press, Cambridge, Mass.Mayr, E.: 1982, The Growth of Biological Thought; Diversity, Evolution, and Inheritance,

Belknap Press, Cambridge, Mass.Richards, R. J.: 1987, Darwin and the Emergence of Evolutionary Theories of Mind and

Behavior, University of Chicago Press, Chicago.Ruse, M.: 1986, Taking Darwing Seriously, Basil Blackwell, Oxford.Ruse, M. and E. O. Wilson: 1986, 'Moral Philosophy as Applied Science', Philosophy 61,

173-192.

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Singer, P.: 1981, The Expanding Circle: Ethics and Sociobiology, Farrar, Straus & Giroux,New York.

Sober, E.: 1984, The Nature of Selection: Evolutionary Theory in Philosophical Focus,MIT Press, Cambridge, Mass.

Tennant, N.: 1983, 'Evolutionary v. Evolved Ethics', Philosophy 58, 289-302.Thompson, P.: 1983, 'The Structure of Evolutionary Theory: A Semantic Approach',

Studies in History and Philosophy of Science 14, 215-219.Wilson, E. O.: 1975, Sociobiology: The New Synthesis, Belknap Press, Cambridge, Mass.