To the Editor:

There is nothing intrinsically wrong with scientists writing outside their fields—the great physicist Erwin Schrödinger’s reflections on biology, for instance, inspired a generation of top-notch biologists. But mathematician David Berlinski’s excursion into evolutionary psychology does little more than muddy some previously clear waters [“On the Origins of the Mind,” November 2004].

The linchpin of Mr. Berlinski’s attack on evolutionary psychology is his suggestion that scholars like Steven Pinker, Daniel Dennett, and myself believe “that human behavior is ‘the product of evolution’” (emphasis added). Only the keenest readers would notice that this notion is drawn from a newspaper story. What the “disputatious group” of scholars identified by Mr. Berlinski actually holds in common is not the overstrong claim that evolution has shaped behavior but the far more subtle idea that evolution has shaped the development of the mind.

As I explain in my recent book, The Birth of the Mind, genes are too slow to participate directly in behavior. Their chief contribution comes “in advance, in laying down and adjusting neural circuitry, not in the moment-by-moment running of the nervous system.” Mr. Berlinski runs roughshod over the distinction between behaviors and the neural structures that create them, and in so doing he ignores the academic discipline that seeks to bridge the two, namely, cognitive neuroscience. By all accounts, human behavior is the product of situations, experience, and our genetic endowment, and it stands to reason that we would not be able to predict it by looking at just one variable.

The real question is whether the genetic influence is worth investigating. Mr. Berlinski seems to doubt this, advocating instead an attitude based on magic, mystery, and awe. But while there is plenty in nature to inspire awe, there is no need to throw up our hands. Hundreds of recent studies show that genes can and do affect mental life, and no serious scholar would doubt that our genes owe much to evolution.

Mr. Berlinski may be right that “the longer the chain of causes, the weaker the links between and among them,” but his suggestion that this state of affairs represents “a conceptual deficiency that we have no way of expressing, let alone addressing” borders on sophistry. The complexity that Mr. Berlinski apparently fears holds as true in the development of the heart as it does in the brain—try, for example, to predict the exact location of capillaries in identical twins.

But we do not need to invoke mystery or magic to explain the development of the heart, and Mr. Berlinski never gives us a cogent reason for thinking that the situation is any different with the brain. Biology may be more complicated than mathematics or the idealized science that Mr. Berlinski longs for, but the fact that something is complex does not mean that it is not lawful.

Gary Marcus

New York University

New York City

To the Editor:

The prospect that centuries of religious, intellectual, and cultural reference points will melt into an unrecognizable new landscape of scientific knowledge understandably provokes unease, visceral resistance, and even alarm in those who sense the magnitude of the coming changes. These feelings are even sharper for evolutionary psychologists, because our work forces us to live within the strange realities of this barely explored new world. This sense of impending dislocation creates an appetite for seemingly authoritative dismissals of the primary claims of evolutionary psychology, which leading intellectual journals accordingly feed. The appeal of these crafted dismissals is that they give permission to intellectuals to think the convenient: that they do not have to deal with this new world, or revise or surrender any of their beliefs or intellectual allegiances because—what a relief—it is a spurious revolution. Time to sleep.

Yet critics typically fail to take the one step that is indispensable to making their criticism authoritative or even germane: they do not actually read the primary literature or know its content, and so doom themselves to arguing with their own confusions, trafficking in myth, rumor, mischaracterization, and irrelevancy. A brief letter can catalog only a few such confusions present in David Berlinski’s essay.

Natural selection is not “a freefloating form of agency” but an observable, well-modeled physical process like osmosis or convection, deductively entailed by the application of set theory to self-replicating physical systems. Mr. Berlinski’s claim that “field studies have proved notoriously inconclusive when it comes to natural selection” betrays a striking unwillingness to expose himself to the primary literature, in which predictions derived from selectionist theories beautifully explain thousands of observations with economy and mathematical elegance.

More substantially, evolutionary psychologists are supposed to be abashed because Mr. Berlinski has held us up to his Procrustean “model for what science should be”—Newton’s use of differential equations to describe mechanical systems—and found us guilty in his imagination of an insufficient use of differential equations. However impressive this is meant to sound to the mathematically untrained, it provokes laughter in practicing scientists, who use a broad array of mathematical and formal tools in their work. It reveals a basic misunderstanding of the nature of science, no more trenchant than criticizing evolutionary psychologists for not wearing lab coats. Sciences progress not by superstitiously aping the surface forms of past successes, but by applying or inventing whatever formal tools are made necessary by the nature of the phenomena under study. The evolved informational and regulatory functions of the brain are better captured by computational formalizations than by differential equations.

Since Newton, a broad array of new mathematical tools has been developed and applied to an enormous range of sciences. Logic, set theory, combinatorics, probability theory, statistics, algorithmics, geometry, information theory, signal-detection theory, control theory, game theory—all play an active role in evolutionary psychology, alongside differential equations. Examples include kinematic geometry in Roger Shepard’s evolutionary approach to psychophysics, which led to his National Medal of Science; frequentist approaches to probability, used by ourselves and Gerd Gigerenzer to explore evolved mechanisms for judging risk; and our reliance on game theory and various standard and nonstandard logics to investigate evolved reasoning programs enabling human cooperation. Much of the edifice of modern science, from the discovery of the genetic code, to biochemistry, cell biology, developmental biology, immunology, neuroscience, zoology, and geology would not pass Mr. Berlinski’s superstitious test, because their rich content is not expressible by differential equations.

Mr. Berlinski’s other major argument is that the findings of evolutionary psychology are essentially “trivial.” This is the standard claim of critics who wish to be evasively deflationary, without having to assume the burden and risk of showing how any specific findings are actually wrong. Although some findings of evolutionary psychologists may turn out to be wrong, the charge of triviality betrays an elementary unfamiliarity with the field.

Here are some nontrivial discoveries. The laws of thought are not the laws of logic, and do not consist primarily of general-purpose, content-free learning rules (as previously believed). Human rationality is achieved though a heterogeneous collection of reasoning specializations, with their own theoretically predicted, proprietary, nonstandard logics (“innate ideas”), whose diverse structures reflect the structures of various enduring, ancestral adaptive problems. The foundation of human economic activity is an evolved neural mechanism specialized for reasoning about exchange. Evidence confirms the predicted existence of a previously unknown mechanism designed to use ancestrally reliable cues to detect close genetic relatives, to intensify family love toward those individuals, and to activate sexual aversion toward them (i.e., Freud had it exactly wrong). The moral sentiments so far investigated have the characteristics predicted by the hypothesis that they evolved as game-theoretic solutions to the adaptive problems posed by small-group interactions.

Other studies have unpacked the evolved functional logic of anger; mapped the cognitive machinery that causes humans to see each other as members of coalitions, showing how this turns on and off the tendency to categorize others racially; and identified theoretically predicted, previously unknown factors that place children at greatly increased risk of physical and sexual abuse. Our colleagues’ research on universals in mating and sexual attraction, which Mr. Berlinski derides as trivial, falsified mainstream anthropological theories and formed the basis of a sweeping explanation of cultural swings in sexual mores (see James Q. Wilson, “Sex and the Marriage Market,” in Commentary, March 2002). More fundamentally still, the theoretical tenets that have ruled the social sciences for the last century—for example, that human mental content is predominantly the arbitrary local product of social conditioning acting on a blank-slate mind—have been decisively falsified.

This is not a trivial harvest for two dozen researchers, working almost entirely without funding for the past two decades. Such a small group would have had no impact if the ideas were not broadly correct, well-grounded in the natural sciences, and theoretically and empirically powerful. Who knows what might be accomplished if the enterprise were ever funded, or if critics felt an obligation to learn its content and report it accurately?

John Tooby

Leda Cosmides

Center for Evolutionary Psychology

University of California

Santa Barbara, California

To the Editor:

To the layman, David Berlinski’s arguments may sound erudite and incisive, but to the scientist they are sophomoric and outlandish. “Natural selection,” he informs us, “is certainly not a force of nature” because the only basic forces of nature are gravitation, the electromagnetic force, and the strong and the weak force. This is like claiming that Hemingway was a poor writer because he used words, whereas we know that the only basic units of written communication are letters of the alphabet. 

Mr. Berlinski tells us that the great biologist Motoo Kimura showed that the bulk of genetic evolution is due to “random drift” rather than to natural selection. This may be true—the strength of selection at genetic loci is still not fully understood—but Kimura and his colleagues never doubted that phenotypic traits that impose fitness costs on their bearers (e.g., the human brain, with its huge energy needs) cannot persist except through natural selection.

Mr. Berlinski’s goal is to criticize the efforts of evolutionary psychologists to treat the human mind as an evolutionary adaptation. But he shows his misunderstanding of the real issue in the following paragraph:

Thus, when Steven Pinker writes that “nature does not dictate what we should accept or how we should live our lives,” he is expressing a hope entirely at odds with his professional commitments. If ordinary men and women are, like [Pinker] himself, free to tell their genes “to go jump in the lake,” why then pay the slightest attention to evolutionary psychology—why pay the slightest attention to Pinker?

The answer is completely transparent: nature strongly affects, but most likely does not determine, what we should accept and how we should live our lives, just as the terrain and climate in which we build our homes affect but do not determine our architectural choices, or as a sculptor’s raw stone affects but does not determine the final creation.

Evolutionary psychology has helped us understand some of the more welfare-threatening aspects of the human psyche, such as our propensity to exaggerate racial and ethnic differences, our susceptibility to obesity, and our excessive attention to gender differences in behavior. Evolutionary psychology has also helped us understand some of our positive qualities, including social emotions, the ethic of reciprocity, the commitment to egalitarian political principles, and the like.

True, many evolutionary psychologists believe that the human mind is completely a product of evolutionary adaptation, and I agree with Mr. Berlinski that this belief is wholly unwarranted. It is not credible to assert that the human capacities to produce mathematical theorems, great art, and sophisticated systems of morality—let alone our desire to pursue truth for its own sake—are simply the product of the same forces that gave rise to the elephant’s trunk and the kangaroo’s pouch.

Unlike Mr. Berlinski, I believe that biological science, including evolutionary psychology, is among the most penetrating and insightful products of human activity. It need not be discredited in a misguided attempt to give the human mind its due.

Herbert Gintis

Santa Fe Institute

Northampton, Massachusetts

To the Editor:

David Berlinski suggests that since the computer is like an abacus, the mind is therefore not like a computer. This confuses the “is” of predication with the “is” of identity, leading to an obvious analogical fallacy. With greater justification one might instead say that the computer is not like an abacus, since it is typically many orders of magnitude faster and has a vastly greater memory capacity. The fact that computers can perform complex functions that were once reserved to human beings derives from just these characteristics. No abacus could operate a robot explorer on the surface of Mars. This is not to say that minds are computers, but that Mr. Berlinski’s befuddled logic contributes nothing to the debate.

Mr. Berlinski also ignores the statistical basis of most arguments in evolutionary psychology. An amusing example is his discussion of the relationship between female fertility and male judgments of feminine beauty. Empirical data show that, in general, men find those women beautiful who are most average. This is not a paradox, since the variance for beauty traits guarantees that most women do not lie at or near the mode for any of them. If beautiful women are most average, they are also likely to be most fertile. Why? Because in a normal distribution, the mean, though uncommon, is still the commonest single result. All else being equal, frequency indicates fitness, which is just another name for differential reproductive success. Men prefer beautiful women for the same reason they pick stocks with a prov- en track record. Even the passions reason inductively.

Karl F. Wessel

Rancho Palos Verdes, California

To the Editor:

David Berlinski nicely surveys the chain of reasoning invoked in evolutionary psychology. My 2004 book What Is Thought? set out directly to provide the missing steps in that chain—in particular, to understand the case for evolutionary psychology at a computational level.

Physics is not the only discipline that has uncovered absolute laws. Computer scientists have discovered laws that regulate what and how computations are possible. These suggest a concrete proposal that answers many of Mr. Berlinski’s questions. Though my argument does not meet his standard of reducing evolutionary psychology to mathematics, it does provide what seems the best available answer to the critical gaps.

Computer scientists have in recent years formalized the philosophical principle of Occam’s razor and shown that it underlies the learning of concepts. A natural conjecture based on this work yields a model of mind as arising from a compact “Occam” program evolved into the genome. One of several surprises is a new picture of the relationship of nature and nurture. Complexity theory suggests that discovery of this Occam program required the massive computational resources of evolution. The genomic program thus discovered then develops mental processes at the level of apes in just months, requiring relatively little computation.

But humans have built a huge computational superstructure on top of what is programmed in the genome. Language is what has made possible this cumulative progress, allowing contributions from billions of individual minds. Thus, while the critical circuitry enabling thought is essentially programmed in the genome, the vast difference between human and ape cognition is explainable in terms of better nurture, which facilitates cumulative program discovery.

Eric B. Baum

Princeton, New Jersey

To the Editor:

David Berlinski sets too high a standard for evolutionary psychology in his otherwise outstanding article. The “model for what science should be” is too demanding for most fields outside of mathematics and the physical sciences. A more reasonable standard is that evolutionary psychology should perform as well as evolutionary physiology. If evolutionary psychology can explain jealousy as well as evolutionary physiology explains the thumb, then it should be accepted until a better explanation is found.

David Wolfe

Monterey, California

To the Editor:

David Berlinski’s criticisms of the simplistic similes and analogies dominating much of “mind science” are apropos. But it should be noted that serious journals of science frequently print papers that do not operate upon the assumption either that the human mind is “like” a computer or that it is “like” other human organs. Of the three similes discussed by Mr. Berlinski, only the assumption that brains (minds) arise through evolution, like the rest of the organism, is a fixture in neural science. And it appears to be the only assumption that preserves the laws of thermodynamics, along with the rest of physics.

I do not believe that there needs to be a dichotomy between mental and physical properties at all, or that thermodynamic considerations will allow it. If one rejects the atomistic view of the mind as being merely the sum of nerve-firings, and instead recognizes that interactions internal to the electrical field(s) associated with nerve-firings may be what consciousness is, then the only difference between the “physical” and the “mental” is that the “mental” actually is the “physical” within the internal interactivity of the electrical field itself. If conscious mental activity is the differential activity of potentials within the electrical field, we need only envision the mental as being in reality what we symbolically and observationally understand a complex electrical field to be. And best of all, one may compare the reports humans make of their internal states with what is externally observed in order scientifically to test such a hypothesis.

I fully agree with Mr. Berlinski that much of what passes for “mind science” is only so much hand-waving. The dominance of such views impedes the consideration of complex models that deal with the differences between symbolic models and actual physical interactivity in the brain. My hope is that Mr. Berlinski’s critique will be understood and taken to heart, so that models addressing the issues he raises will be seriously studied and further developed.

Glen Davidson

College Place, Washington

To the Editor:

To describe the virtues of David Berlinski’s articles in Commentary on the reigning orthodoxies and received wisdom of so many scientists would make for a very long letter indeed: vivid images, effective tropes, unrivaled knowledge of the literature, sure grasp of the issues. But what I most appreciate about Mr. Berlinski’s essays (and I say this, paradoxically, as a professional theologian) is that in the dialogue between religion and science, he wisely leaves religion out of the picture. Other writers spot similar contradictions in materialist accounts of science. But too many of them overreach and see these antinomies not just as a warrant for theology (fair enough) but also as a warrant for their arguments about what science should say instead of materialism.

My only puzzle about Mr. Berlinski’s most recent essay is why he stopped short in his administration of the coup de grâce to the neurological materialists. Yes, “[a]t some time in the history of the universe, there were no human minds, and at some time later, there were.” But that truth only counts when these minds are thereby forced to say as well, “at some time in the history of the universe, there were no human minds, and later I became aware of my mind.” In other words, minds (and primitive sensations, too) only come into being as a first-person reality: no sensation without a sensor, and no mind without an “I” to be a mind of.

The first-person nature of the mind is something about which science can in principle have nothing to say. In philosophy this ineluctable “first-person-ness” is known as “perspectivalism” (or what Martin Heidegger called “thrownness”). I prefer to call it the “Why me?” question. Why was I not born as Cleopatra’s maid, or Cicero’s pedagogue, or a peasant working on the estate of Charlemagne, or even as my sister? How can any psychology, Darwinian or otherwise, explain that enigma?

The point behind these various terms is that no one chooses to be born. We cannot choose our sex, our parents, our race or nationality, or even to a large extent our personality and character. Even if, per impossibile, computers were made to think, a truly thinking computer would soon be asking, “Why wasn’t I born a rat, a cat, or a bat?”

Science has always been forced to stop dead at that threshold—at just the point, in other words, where religion takes over.

Rev. Edward T. Oakes

University of St. Mary of the Lake

Mundelein, Illinois

David Berlinski writes:

According to Gary Marcus, I erred in assigning to evolutionary psychologists the thesis that evolution has shaped the development of human behavior. The “far more subtle” thesis he himself champions is that evolution “has shaped the development of the mind.” But I assigned no such view to Mr. Marcus, nor did I endorse it myself. My essay was about the human mind, just as its title asserted; in recapitulating the chief doctrines of evolutionary psychology, I quoted Mr. Marcus referring to the mind as the “organ of thought and language.”

Nevertheless, if “evolution has shaped the development of the mind,” it does follow that human behavior is the product of evolution as well—at least to the extent that evolutionary psychology has a real claim on our attention. What Boron salts do, I observed in my essay, is determined by their chemical structure; if what human beings do is not determined by their mental structure, then the mind is not the source of their actions.

I do not in the least doubt that “genes can and do affect mental life”; so can and so does the liver, and often more dramatically. But nothing in what I have ever written can be taken as suggesting that I am busy “advocating an attitude based on magic, mystery, and awe.” Far from celebrating the powers of the night, I deplored them as “depressing”; I am an advocate of the light, as readers of my work are well aware.

Commenting upon my analysis of the second simile embraced by evolutionary psychology—that the mind is like any other organ of the body—Mr. Marcus discerns “sophistry”; he does so by neglecting to cite properly what I wrote. Referring to nine examples of progressively inflated rhetoric, I remarked that they “suggest that the longer the chain of causes, the weaker the links between and among them.” According to Mr. Marcus, I then characterized this state of affairs as “‘a conceptual deficiency that we have no way of expressing, let alone addressing.’” In fact what I wrote was rather more circumspect: “Whether this [state of affairs] represents nothing more than the fact that our knowledge is incomplete, or whether it points to a conceptual deficiency that we have no way of expressing, let alone addressing—these are matters that we cannot now judge.” My words were disjunctive and inconclusive.

Then there is Mr. Marcus’s comparison of the heart with the brain. He is persuaded that just as we can imagine a complete causal pathway leading to the formation of the human heart, so we can imagine a complete causal pathway leading to the formation of the human brain. But if the human mind is understood as a physical organ, it becomes very difficult to keep sight of its astonishing properties—the very ones I cited at the beginning of my essay. If, on the other hand, the human mind is understood as the source of language, cognition, and sentiment, then it becomes very difficult to imagine a complete causal chain leading to its formation.

Those difficulties are not simply matters of detail. We cannot rationally determine whether the human mind is the expression of information contained in the human genome until we have properly characterized its properties. This is something that plainly we are not yet in a position to do. (For further elucidation, see my article on the evolution of the mammalian eye, “A Scientific Scandal,” in the April 2003 Commentary, and the subsequent exchange with readers in the July-August issue of the same year.)

John Tooby and Leda Cosmides suspect that “unease” and even “alarm” are what prompted my “seemingly authoritative” dismissal of evolutionary psychology. I assure them I need neither unease nor alarm in order to seem authoritative. Unlike some of my other recalcitrant organs, my spleen retains its preternatural grandeur.

Having taken up a third of their long letter in pointless complaints, Tooby and Cosmides conclude— naturally enough—that the remaining two-thirds are insufficient to provide readers with a “full catalog” of my confusions; a partial list must do. Curiously enough, although that list conveys a rich sense of their own indignation, it fails to include either detailed arguments or specific references to the literature.

It would have made for an improvement in understanding, not to mention communication, if my correspondents had accurately represented those of my arguments they are eager to dismiss. For example, I did not for a moment suggest that evolutionary psychologists should busy themselves with differential equations, or occupy themselves in “superstitiously aping the surface forms of past successes” (although some judicious aping on their own part would not be amiss). What I proposed to do was to compare evolutionary psychology with “the model for what science should be,” the better to see the slippage that resulted. My conclusion, of course, was that there is plenty of slippage to be seen, but how traction is to be recovered is not my concern. I am not, after all, an evolutionary psychologist.

As for their other complaints: in a long passage beginning with the words “Here are some nontrivial discoveries,” and ending two paragraphs later with the words “have been decisively falsified,” Tooby and Cosmides survey the chief accomplishments of their discipline, and find them good. They do this because they are under the impression that I have dismissed their own research as trivial. But that is a misunderstanding. I did not discuss their work at all, and the word “trivial” does not occur in my essay; neither does the judgment that it might express.

Tooby and Cosmides are on more faithful textual grounds in observing that I dismissed evolutionary field studies as “notoriously inconclusive.” They are, and I did. Consider, for example, the field studies undertaken after the publication in 1986 of J.A. Endler’s well-known treatise, Natural Selection in the Wild. In the years since, any number of biologists have been trooping off to grim, inhospitable places in order to consider natural selection where it is supposed to be working. Reviewing the recent literature in a survey titled “The Strength of Phenotypic Selection in Natural Populations,” J.G. Kingsolver, H.E. Hoekstra, D. Berrigan, S.N. Vignieri, C.E. Hill, A. Hoang, P. Gilbert, and P. Beerli—a veritable regiment of researchers—discussed 63 published field studies dealing with 62 species. Their conclusions may be found in the March 2001 issue of the American Naturalist.

In their abstract, Kingsolver et al. write that “most published selection studies were unreplicated and had sample sizes below 135 individuals, resulting in low statistical power to detect selection of the magnitude typically reported for natural selection.” (In a selection study based on 134 individuals, they write, in which the linear selection gradient is 0.02, “the probability that one could reject the null hypothesis of no selection at the 95-percent level is less than 50 percent.”) When larger sample sizes are considered—greater than 1,000— the statistical picture is more sobering still. “Our most powerful studies,” Kingsolver et al. write, “indicate that selection is weak or absent.” Inconclusive enough?

Finally, I am as eager as Tooby and Cosmides to assume my rightful place at the funding trough, and I believe my prospects would be improved if only they got out of my way.

Scientists, Herbert Gintis writes, are apt to find my arguments “sophomoric and outlandish.” But it would appear that he himself agrees with my conclusions—at least to the extent of affirming that “the belief that the human mind is wholly a product of evolutionary adaptation is . . . wholly unwarranted.” Well, to quote Miguel de Unamuno, “Si un hombre nunca se contradice, será porque nunca dice nada” (if a man never contradicts himself, this can only be because he never says anything at all).

I argued in my essay that if natural selection is a force, then it is certainly not a force of nature. Acting as witness for the prosecution, Mr. Gintis demurs. Just as words are made up of letters, so natural selection is made up of elementary forces. This analogy will seem compelling only if some description of natural selection as a force can be derived from a description of its constituent physical elements. But that cannot be done. As for the characterization of Motoo Kimura’s position that Mr. Gintis offers, not only do I agree with it but, acting preemptively, I said as much in my essay. Kimura, I wrote there, “is willing to accept the Darwinian disjunction: either complex adaptations are the result of natural selection or they are the result of nothing at all.”

In asserting that “nature strongly affects, but most likely does not determine, what we should accept and how we should live our lives,” Mr. Gintis has rediscovered the usefulness of Ptolemy’s concept of influence. It is a discovery that Thomas Aquinas made as well. “The stars,” he wrote, “cannot be the direct cause of the free will’s operation”: since the will is not a material object, it cannot be the effect of a material cause. Nevertheless, the stars serve as “an inclination” to those operations. In place of the stars, evolutionary psychologists, and Mr. Gintis along with them, have now substituted the genes. The result is a familiar form of incoherence, if one that has to be abandoned as soon as genetic accounts are clear enough to be tested. We are not inclined to see what we do see. We have no choice in the matter.

The improvements in understanding that Mr. Gintis attributes to evolutionary psychology were not properly the subject of my essay; still, no matter how generously its conclusions are interpreted, I find it mystifying that he discerns among them “a commitment to egalitarian political principles.” As for whether the biological sciences are “among the most penetrating and insightful products of human activity,” I could not agree more; my own appreciation for them is exceeded only by my eagerness to make use of their discoveries before it is too late to derive benefit from them.

Karl F. Wessel is quite wrong about the computer and the abacus. The idealized abacus has precisely the power of a Turing machine. Details may be found in chapters 6 and 7 of the third edition of George S. Boolos and Richard C. Jeffrey’s Computability and Logic.

The remarks Mr. Wessel advances about beautiful women suggest an alarming indifference to the facts of life. Great beauties are not counted great beauties because they look like other women. They are beautiful precisely because they do not. But whether average or extraordinary, beauty has virtually nothing to do with fertility. The overwhelming majority of women between the advent of puberty and the onset of menopause are fertile, and those who are not fertile fail to reveal their deficiency by means of visible hormonal markers.

In his friendly letter, Eric B. Baum suggests that my reservations about evolutionary psychology might best be addressed by a close reading of his own book, What Is Thought? Since I have not yet done so, I cannot comment in detail; but his letter does not inspire me to order a copy.

Specifically, I do not understand what Mr. Baum means when he suggests that Occam’s razor underlies the learning of concepts, or what he means by saying that the “Occam program required the massive computational resources of evolution,” or for that matter what he means by the “computational resources of evolution” (a phrase that suggests Daniel Dennett’s celebration of natural selection as an algorithm, and seems to have about as much content), or how the “genomic program thus discovered then develops mental processes at the level of apes in just months.” Of course, the fault may well be my own: too much time spent watching television and not enough reading the edgy new literature.

I am perfectly willing to accept David Wolfe’s suggestion that evolutionary psychology should meet the standards of evolutionary physiology, but insofar as the latter discipline could be judged successful, it would be because it met precisely the standards I have set. But in fact I do not believe that evolutionary physiology meets those standards at all, which makes me willing to press the comparison between the two disciplines to the bitter end. It would be far more reasonable to argue that both psychology and physiology should meet the same standards. For the moment, they do not. If and when they did, that would still leave unexplained the origin of both the major physiological and the major psychological systems.

I appreciate but cannot completely endorse Glen Davidson’s remarks. “[O]nly the assumption that brains (minds) arise through evolution . . . preserves the laws of thermodynamics,” Mr. Davidson writes. If by evolution he means nothing more than some physical process or other, then yes, it is trivially true that only a physical process could possibly preserve the laws of thermodynamics. But if by evolution he means a Darwinian process of random variation and natural selection, then it is by no means clear that other physically plausible alternatives might not exist.

That is one problem. A second follows when Mr. Davidson lets light slip between the brain and the mind. If he means to argue that the brain as a physical structure must respect the laws of thermodynamics, I cheer him on; but if the mind and the brain prove in the end to be hopelessly distinct, then plainly thermodynamic considerations will play less of a role than he conjectures. A physical theory applies, after all, to physical objects. In the past half-century, both philosophers and cognitive scientists have displayed an almost indecent eagerness to separate themselves from any form of Cartesian dualism. Nevertheless, Descartes’ ghost keeps shambling on in their pursuit and, even more remarkably, often has interesting things to say.

In the balance of his comments, Mr. Davidson seems to be continuing another tradition in cognitive psychology (and analytic philosophy as well), one involving the dismissal of precise descriptive detail in our accounts of mental life and their replacement by rhetorical categories so general as to be virtually scholastic. What does it really mean to say that consciousness may be identical to “interactions internal to the electrical fields associated with nerve firings”? I have no quarrel with those electrical fields; but before any identification can be made between fields and consciousness, surely we have some right to an explication of what consciousness is? Unfortunately, the moment such an explication is undertaken, a gabble of incomplete metaphors, corrupt similes, and half-formed intuitions compete for attention.

Thus, when Mr. Davidson talks of “conscious mental activity,” is consciousness an attribute that one can peel off from a mental act itself, like the skin from an orange? Or is it rather that consciousness and act are indissoluble, now and forever? Very often we speak of consciousness when we wish to convey a heightened state of awareness. This might suggest that in some circumstances it reflects attention paid to previously overlooked mental states, as when we become suddenly conscious of fear, embarrassment, or even hunger. But we may certainly be aware of certain states or even sensations without being conscious of them. It makes perfect sense to speak of an unconscious awareness (of danger, for instance), but no sense at all to speak of an unconscious consciousness.

I may be conscious of my thoughts, my memories, my aches and pains, or my clothes; I may be conscious as well of my past, my age, my rights, my pronunciation of French, my standing in the community, my real feelings, or my unwillingness to sign a questionable legal document. The word, and the concept it denotes, open up to a vast spider web of intricate associations and remarkably delicate distinctions.

Consciousness itself? Who knows what it is, or even whether it is important?

I very much appreciate Father Edward T. Oakes’s efforts to describe the virtues of my essay. I am also sympathetic to the philosophical considerations that he introduces, to the extent that I understand them—but only to that extent. I suppose we do know our minds from the inside out, but in saying that I know my own mind, am I committing myself to the view that I am one thing and what I know is another? In finding an “enigma” in the question of why he was not born Cleopatra’s maid, Father Oakes has neglected to consider the possibility that the question is incoherent because the situation he suggests is impossible. These subtle and difficult issues are discussed in Saul Kripke’s Naming and Necessity.

In a more general sense, I would contend that it is hardly necessary to look to the mind for the place where the physical sciences stop. The physical sciences are quite capable of coming to a stop all on their own.