PINKER: Many points that Professor Rose has made puzzle me, because I don't understand what they have to do with any of the theses of evolutionary psychology or How the Mind Works. The claims that "we're not infinitely flexible," that there are no "empty organisms," that organisms are "open systems organized in four dimensions," "self-organizing," "are not just naked replicators," "actively select their options," "interact with their environment," "should be understood at multiple levels," "are dynamic," are "not passive victims," "are not indefinitely flexible," and so on-all these are points that I completely agree with, and I don't understand what the point of Professor Rose's argument is.

Let me concentrate, then, on more substantive points. Number One: Our own ability to defeat the metaphorical designs of our genes, such as choosing to remain childless, has nothing to do with Cartesian dualism, and I explain in How the Mind Works where they do come from. The mind is composed of many parts. One part is sexual desire; another part is an ability to apply cause and effect reasoning to the world. In the world we live in now, we have available to us contraception, which was not available in the world in which we evolved. One part of the mind, the part that figures out that one can have the pleasures of sex without necessarily having children, can be applied today in a way that would not have been possible as we evolved. That's a purely mechanistic, non-Cartesian explanation.

Second, about reverse engineering. It is NOT the empty exercise that Professor Rose hinted at. As Ernst Mayr, someone that Professor Rose quotes approvingly, points out, if it were not for the adaptationist program, or reverse engineering, we would still be ignorant about what most of the parts of the body do, such as the spleen. The science of physiology was born when Harvey reverse-engineered the circulatory system by noticing that there are valves in the vein and that they must be there to help the blood circulate.

In the case of psychology, the reverse engineering can work if one does it in two steps. First, do the psychology that characterizes the properties of an aspect of the human mind. Second, have an INDEPENDENT optimality analysis of the domain in question that could characterize-completely independently of our study of the mind-what the optimal solution to an adaptive problem would be under the constraints available. That can come from optics in the case of vision; from dynamics and kinematics, in the case of motor control; from the theory of computational systems, in the case of memory, and so on. It's the degree of fit between the independent optimality analysis and the empirical facts of the mind that break the circle and make reverse-engineering something other than just-so story telling.

Number Three: Professor Rose ridicules my allusions to life in the Stone Age. In fact it is not a fantasy of a Flintstones way of life, but simply points out obvious historical facts-and Professor Rose rightly emphasizes the importance of history-such as that many of the features of life today that we take for granted had a recent historical origin and could not have been part of the environment in which we evolved, such as written language, contraception, police, court systems, formal education and, so on. One can come up with surprising hypotheses based on these minimal and noncontroversial assumptions about the difference between the world that we live in now and the world in which we evolved.

Fourth, it is not true that I suggested that the only form of love is love of spouses, which I suggested was a way of cherishing the other person who has as much at stake in one's children as one does oneself. I also talk about long-term companionate love, as would be found in a pair of close friends, and about the love of family. He refers to our ability to love non-biological offspring; well, there is an empirical prediction that the love of biological offspring is not the same as love of non-biological offspring, and Martin Daly and Margo Wilson have done an extensive set of studies showing that indeed those two forms of love are not the same. Their analysis of the different patterns of love and abuse of biological children versus step-children bears out the hypothesis that those are different kinds of love. But I have to stop now.

ROSE: Let me just pick up a couple of points in Steve's response. He says that our ability has nothing to do with Cartesian dualism. He it is who wrote that if the genes don't like what he does they can go jump in the lake. I didn't say that. He wrote it. Now where did these different parts of the mind that he's talking about and which conflict with one another come from if they're not generated as the result of interaction between genes, the cells and the environment during the wiring or development of the brain? Materialism has to insist that our genes have to do with everything; they have to do with both, if you like the genetic urge to reproduce that he described, and the desire to have sex without reproducing that he described as the advantage of contraception. That's where materialism comes in, and that's where my challenge to him of being a Cartesian endures, because it's precisely where he wants to let the mind, or these different bits of the mind float free, that I won't accept.

Now we come to the issue of reverse engineering. He's quite wrong when he says that physiology was studied by reverse engineering; when William Harvey likened the pumping-the workings of the heart-to the workings of a pump, this wasn't reverse engineering, he was drawing a metaphor as to how you could understand the mathematics of heart function. It was a tremendously revealing and important metaphor. The problem we have in science, particularly in biology, is to distinguish between metaphor, like that, which gives you mechanical properties; analogy, when we say that a brain is like a computer, which can be very misleading in a variety of ways on which both he and I would agree; and strict homology, when we say that a process is evolutionarily developed and depends on mechanisms that are identical in our reptilian ancestors and ourselves,. The mistake that evolutionary psychology makes in this reverse engineering discussion is constantly to mistake metaphor and analogy for homology, and draw what I regard as both horrendous scientific and horrendous political conclusions from it. Finally, love-oh dear, that really won't do, Steve, you were the person again on Start the Week who explained love in terms of shared the genetic interest that you and your partner had in the rearing of offspring. You were indeed challenged on Start the Week about why you yourself chose to remain childless, and I think you handled that perfectly appropriately. But what I'm trying to insist is that the term love cannot be reduced simply to that shared genetic interest. It cannot I think even be sensibly argued to have arisen homologously as a result of evolutionary processes which indeed produce a shared genetic interest in all of us in our offspring. Human life, human society, is much much richer than these travesties. And I do insist that what you offer is a Flintstone type travesty of life today. I really won't buy the Daly and Wilson argument about infanticide. I suspect that there is a wealth of criminological knowledge which sort of makes much better sense than this one study that you and your evolutionary psychology colleagues constantly quote in order to boost this particular argument.

Part II - Q&A to follow