Over at HuffPo, Professor Matt Rossano, Head of the Department of Psychology at Southeastern Louisiana University, has posted a thought-provoking article entitled, “Thomas Aquinas: Saint of Evolutionary Psychologists?”
Let me say at the outset that Professor Rossano is a very fair-minded scientist, who has made a genuinely sympathetic attempt to answer the question, “How did religion come to be?” from a secular perspective. In his recent book, Supernatural Selection (see here for a brief synopsis and here for a look inside the book), he acknowledges that “religion is vitally important to morality” and that “religion does make us more moral,” although he strongly disagrees with the notion that without religion there can be no morality (and he argues that Aquinas did, too). Provocatively, Rossano even goes so far as to say that “Religion made us human.” Statements like these clearly put him at odds with the New Atheism of Richard Dawkins, author of The God Delusion.
In his latest article, Professor Rossano discusses the thought of St. Thomas Aquinas, and argues that in many ways, Aquinas anticipates the principles used by evolutionary psychologists today to explain human behavior. Rossano focuses on the institution of marriage, and shows that many of the concepts which figure in “parental investment theory” – a theory invoked by evolutionary biologists to explain parental behavior in the animal world – can also be found in Aquinas’ discussion of marriage, in his Summa Contra Gentiles, Book III, question 122. He goes on to argue that Aquinas, if he were alive today, would be an evolutionist, and in the title of his article, even goes so far as to nominate him as the patron saint of evolutionary psychologists!
To his credit, Professor Rossano gets a lot right about Aquinas: most of his factual assertions about Aquinas’ philosophical views are correct. However, his attempt to marry Aquinas’ thinking with evolutionary psychology is doomed to failure. Here’s why.
Rossano’s argument founders on the rock of Aquinas’ deep-seated commitment to essentialism, which pervades his moral and theological thinking. Most readers will be aware that I recently posted a lengthy online reply to claims made by Professor Michael Tkacz, Associate Professor of Philosophy at Gonzaga University, to the effect that there is no philosophical conflict between Thomism and Darwinism. In the first part of my five-part reply, I provided a summary of Aquinas’ thinking on the origin of living things, including human beings. One of the things I highlighted was Aquinas’ essentialism, which for Aquinas entailed that the evolution of one kind of animal into another is an impossibility. Professor Rossano is well-acquainted with Aquinas’ thinking, however, and in the opening paragraphs of his article, he acknowledges that Aquinas was a creationist who believed that species were fixed and unchangeable, although he later argues that Aquinas, with his well-trained, inquisitive mind, would have given up this belief, if he were alive today.
But this casual rebuttal simply won’t do. In the second part of my reply to Professor Tkacz, I summarized what I saw as four decisive reasons why Aquinas, even if he were alive today, could not have embraced Darwinism:
(i) his essentialism;
(ii) his religious belief that living creatures of every kind were perfectly made, in relation to their biological ends;
(iii) his insistence that God and Nature make nothing in vain (hence there are no redundant organs or body parts in any kind of living organism); and
(iv) his claim that for each and every kind of organism in the natural world, each and every one of its characteristic features was personally designed by God.
I also presented documented quotations from Aquinas, showing that he taught all four tenets listed above, in Part One of my reply to Tkacz. Thus even if one were to argue (as Professor Rossano does) that Aquinas, with his scientifically curious mind, would cast aside his essentialism if he were alive today, there still remain three major theological hurdles, which would have prevented Aquinas from endorsing the neo-Darwinian theory of evolution. Professor Rossano does not appear to be aware of these.
Playing devil’s advocate, I then anticipated how a so-called “modern Thomist”, wishing to reconcile Aquinas’ thought with the scientific claims of neo-Darwinian evolution, might attempt to “reinterpret” Aquinas’ essentialism to make it more Darwin-friendly, and I then rebutted this modernistic attempt to rewrite Aquinas. I also argued that Aquinas’ claim that the world contains exactly the right amount of natural evil is fundamentally opposed to the neo-Darwinian claim that living things originated as a result of memoryless Markov processes, which are inherently blind to any long-term goals – let alone cosmic goals, such as obtaining exactly the right balance of evil in the world. If God wanted to achieve goals like that, then He would have to guide the process of evolution. This means that if you wish to be a Thomist, you have to believe in some version of Intelligent Design, at the very least.
But what I’d like to talk about in today’s post is Aquinas’ theory of morality, which is permeated with essentialism. And it is glaringly apparent, in the very passage cited by Professor Rossano! For what Aquinas taught was that no human action could be moral for a person in virtue of any special circumstances accompanying his/her act. An action could only be moral if it would be all right to do it, in the general circumstances that characterize that act, when performed by the human species as a whole. This is made clear in Aquinas’ discussion of whether a wealthy woman, who was capable of taking care of her child if she became pregnant, would be morally justified in having sex outside marriage. Aquinas’ answer is a very firm “No”:
 Nor, indeed, is the fact that a woman may be able by means of her own wealth to care for the child by herself an obstacle to this argument. For natural rectitude in human acts is not dependent on things accidentally possible in the case of one individual, but, rather, on those conditions which accompany the entire species. (Summa Contra Gentiles, Book III, question 122, paragraph 7.)
Aquinas’ reference to “those conditions which accompany the entire species” underlines the pivotal importance of essentialism to his ethical thinking. For if there are no such things as fixed natural kinds (which Aquinas calls “species”), then neither can there be any fixed, universal moral norms.
“But biological species do evolve over time!” I hear Professor Rossano insisting. And I don’t deny it for a moment. If Professor Rossano wishes to examine my argument as to why this fact doesn’t overturn essentialism, then I would invite him to click here. In a nutshell: there is ample evidence (summarized in Professor Michael Behe’s book, The Edge of Evolution and additionally attested by other biologists), that living things do indeed belong to clearly distinct kinds, that there are built-in natural limits to evolutionary change, and that these limits roughly coincide with the scientific taxon we now call “family,” rather than the taxon we call “species.” Essentialism is not dead; it’s just moved up two taxonomic levels, that’s all. (I also argue that human beings belong to a different natural kind from chimps.)
Getting back to St. Thomas Aquinas: in paragraph 9 of same passage that Professor Rossano quotes from, Aquinas considers the morality of contraceptive acts, which are designed to avoid the hazard of creating a human being that one cannot take proper care of, and which are therefore invulnerable to arguments attacking fornication because it leads to irresponsible procreation. However, Aquinas opposes contraception as contrary to natural law. He is, of course, well aware of the common riposte to natural law arguments against contraception, that if using one’s genital organs in an “unnatural” way for pleasure outside of marital acts is immoral, then so is the act of using other bodily organs in “unnatural” ways – e.g. using your hands for walking (as acrobats do) – which is manifestly absurd. Aquinas then proceeds to refute this argument. He argues that nothing harmful for the human species as a whole follows from people using their hands for walking, if they so choose; but people’s use of their genital organs for pleasure outside marriage whenever they felt like it, would interfere with the good of “the preservation of the species.” (For those who find Aquinas’ reasoning unconvincing on this point, I should mention that his argument has been much more rigorously formulated by contemporary natural law moralists – see here, here, here and here for examples.) In any case, the point I wish to make here is that Aquinas’ reasoning, with its underlying commitment to the preservation of the species, clearly presupposes essentialism.
Aquinas does not flinch from drawing the logical conclusions of his natural law argument against contraception, which I shall quote in full:
 … Hence, after the sin of homicide whereby a human nature already in existence is destroyed, this type of sin appears to take next place, for by it the generation of human nature is precluded.
 Moreover, these views which have just been given have a solid basis in divine authority. That the emission of semen under conditions in which offspring cannot follow is illicit is quite clear. There is the text of Leviticus (18:27-23): “You shall not lie with mankind as with womankind… and You shall not copulate with any beast.” And in 1 Corinthians (6:10) : “Nor the effeminate, nor liers with mankind… shall possess the kingdom of God.”
 Also, that fornication and every performance of the act of reproduction with a person other than one’s wife are illicit is evident. For it is said: “There shall be no whore among the daughters of Israel, nor whoremonger among the sons of Israel” (Deut. 23:17); and in Tobit (4:13): “Take heed to keep Yourself from all fornication, and beside Your wife never endure to know a crime”; and in 1 Corinthians (6:18): “Fly fornication.”
 By this conclusion we refute the error of those who say that there is no more sin in the emission of semen than in the emission of any other superfluous matter, and also of those who state that fornication is not a sin. (Summa Contra Gentiles, Book III, question 122, paragraphs 9-12.)
This is the man you wish to nominate as the Patron Saint of evolutionary psychology, Professor Rossano? Somehow I don’t think too many of your Darwinist colleagues are going to agree with you!
Aquinas’ ethical reasoning in the passage cited above provides a splendid example of why Thomism and Darwinism don’t mix. Need I say any more?