Why Do Moral Theologians Need Evolutionary Psychology?

How many times have you heard someone evaluate some moral matter with the words “it’s just not natural?”  Even in the most progressive, tolerant societies put some limit on human action (e.g. bestiality, pederasty, homosexuality, cannibalism, suicide) based on what is “natural.”  Additionally, since the middle of the twentieth century, societies have moved from what is “natural” to natural human rights like the protection against slavery, social persecution, and injury to person or property.   In moral theology, the way to talk about these negative and positive precepts is through natural law.

Natural law has an extensive history in the field of ethics, and within Christianity, the field of moral theology.  The Stoics, the Jewish philosopher Philo, Cicero, the neo-Platonists, the early Church theologians Origin, Ambrose, and Augustine, and even the apostle Paul used some form of natural law to reflect on human behavior.  The Stoic concept of natural law was that “universal nature” was equivalent to “universal reason,” and so by commanding people to live in accordance with nature, they were commanding them to live in accordance with right reason or universal law.  For the Stoics, there is an inherent structure in the cosmos which is empirically available to human beings through their reason.  All subsequent reflection on natural law is some sort of variation on this Stoic concept, namely that there is an order to nature which dictates a certain way of existing.

Over the centuries, natural law reasoning became simplified to basically say that, for humans, “biology = morality.”  Homosexuality, for example, could be condemned under such reasoning through the simple argument that biologically, human genitalia was naturally meant to combine with the opposite sex for the production of offspring.  In other words, pre-rational aspects of our human nature (our biological construction) set clear prohibitions on human behaviors which violated natural operations of biological processes.  The most readily available examples were sexual and so natural law was frequently used to justify and condemn specific sexual practices.

In the twentieth century, this sort of simplistic natural law reasoning fell out of favor under the influence of the analytic philosophers like G.E. Moore and evolutionary biologists.  G.E. Moore famously refuted what he called the “naturalist fallacy” that one could argue from and “is” to an “ought.”  What he meant is that it is philosophically unsound to say that just because something is a certain way, it does not follow that a thing is supposed to be that way.  Evolutionary biologists further undermined natural law reasoning by calling into question whether there was any definite human nature at all, and if there was, it was simply the result of natural selection without any normative force.

However, the concept of human nature cannot be dismissed too quickly.  First of all, moral norms grounded in human nature are clearly advantageous in our global society where we want to articulate “universal moral norms” as dictated in the U.N. Declaration of Human Rights.  If moral norms are grounded in human nature, they are accessible to all people in all cultures which means that we can make universal moral judgments like “slavery is morally forbidden” or “genocide is immoral.”

Moreover, as I implied earlier in this essay, we all have a “sense” of what is natural for human beings and therefore a sense  of what should be encouraged or prohibited.  Few people would look at a person committing bestiality without some element of repugnance or disgust.  One of the first phrases that children can articulate is “that’s not fair,” meaning they have a sense of what is fair, which is related to what is natural.  This is where evolutionary psychology comes into play.

Evolutionary psychology is a rapidly expanding field of scientific research built on the idea that human behavior can be explained by evaluating “species-specific nature.”  Applied to questions of morality, evolutionary psychology seeks to explain our moral intuitions and instincts.  As Steven Pinker wrote in an article for the New York Times Magazine, “The human moral sense turns out to be an organ of considerable complexity, with quirks that reflect its evolutionary history and its neurobiological foundations. . . . dissecting moral intuitions is no small matter. If morality is a mere trick of the brain, some may fear, our very grounds for being moral could be eroded. Yet, the science of the moral sense can instead be seen as a way to strengthen those grounds, by clarifying what morality is and how it should steer our actions.”

Pinker illustrates in his article how different studies in the field have shown how moral intuitions precede rationalization.  One interesting example comes from psychologist Jonathan Haidt (from my alma mater the University of Virginia) who studies the psychological foundations of morality.  Haidt studied the responses of people to a hypothetical case of incest where a brother and sister decide to have sex one night.  They double up on birth control to prevent contraception, they both enjoy the sex so there is no harm to their own psychological states, and they keep the event a secret so there is  no harm to the community.  Still, overwhelmingly, people describe this action as wrong, even though they can’t explain exactly why.

Another interesting example devised by Philippa Foot and Judith Jarvis Thompson is the Trolley Problem.  In this scenario, the majority of people studied would flip a switch to send a trolley careening toward five  people off the track, even though it would kill the trolley driver, but would not push a fat man onto the tracks in order to stop the trolley.  In the two cases, the balance of life lost and saved is the same (one lost but five saved), but something in our brain keeps us from sanctioning the manhandling of an innocent bystander.

The significance of these studies for ethics and moral theology is that they again raise the question of whether there is something called a “human nature” and a corresponding natural law.  Marc Hauser and others, for example, have argued that human beings have a universal moral grammar that allows us to articulate the wrongness of certain actions like murder and rape.  Others have argued that there may be a genetic basis for things like altruism in the same way that there may be a genetic basis for anti-altruistic modes of existence like with psychopathy.  Of course, Richard Dawkins has famously argued the opposite, namely that human beings are genetically-oriented to be selfish, not altruistic.  Neither side has conclusive empirical evidence but they day is not too far away when we may be able to look at the human genome and figure out why we act the way we do, and what the genetic basis for our moral conclusions is.

Moral theologians and ethicists need to keep their fingers on the pulse of such studies and must stay up-to-date in the field of evolutionary psychology and biology as well as related fields like neuropsychology.  I tend to think that there is  something called a human nature and that these empirical studies lend insight into what that human nature is.

However, a cautionary note is in order.  It would be a mistake to take these studies and again make the mistake of arguing from “is” to “ought.”  Human beings are rational creatures, capable of reflecting on human behavior and not just acting from instinct or intuition.  The examples from Jonathan Haidt and Philippa Foot and Judith Jarvis Thompson illustrate how our moral instincts work pre-rationalization.  These studies are significant, but for ethicists and moralists, they don’t give us the last word.  Ethicists and moralists must ask why we think that incest is wrong, even if there are no bad consequences, and whether that instinct should be codified into a rationally formulated norm.  But it would be a mistake to lapse into some sort of biological determinism in light of studies that illustrate the empirical basis for a universal human nature.

Nevertheless, the new science of evolutionary psychology is a fascinating and important field for moralists and ethicists as they reflect on the evolutionary processes and psychological mechanisms that form the biological basis for our morality.  I am quite confident that it is in the spirit of Thomas Aquinas that I wholeheartedly and enthusiastically welcome the intersection of morality and evolutionary psychology as a way of better informing both fields and thereby coming to greater knowledge of the moral truth.  But it is also in the spirit of Aquinas that I reject the conclusion that empirical studies about morality allow us to reject moral rationalization and go with our instincts.   As Aquinas says, man is distinct from irrational animals and likewise in the image of God because he is the “principle of his actions, having free will and control of his actions.”  Moralists must make good use of evolutionary psychology without falling once again into the naturalist fallacy.

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3 comments so far

  1. Nando on

    My understanding is that evolutionary psychologists do indeed posit a distinct, but cumulatively selected, human nature, with “selfish” genes creating altruistic people.

    As social creatures, a complex emotional sense could evolve as the eye did–with cumulative advances. Many generations of living among kin and group has done that in our species.

  2. everydaythomist on

    Much of what evolutionary psychologists posit is hypothetical. This is also the case with the idea of “selfish genes.” Dawkins has a gene-centered theory of evolution (he’s not the first one to have such theory, but he is the most famous) which argues that genes get passed on by serving their own interests (i.e. being replicated). The genes themselves are not actually selfish, but they seem like it from our perspective. These genes are then responsible for all types of behavior including altruistic behavior like a mother caring for her young, even to the point of self-sacrifice. The reason, Dawkins argues, that “selfish” genes and altruistic behavior go hand in hand is that the genes responsible for the behavior want to get replicated in future generations and so the self-sacrifice of one organism, if it perpetuates the genes of that organism, serves the goal of the “selfish genes.

    The standard criticism of this idea is that genes might not be the unit of evolutionary selection. Others (like David Stove) think that the role of natural selection (pace Dawkins) has been overstated in higher animals. I don’t know enough about these critiques to have a highly-informed opinion, but I do think it quite likely that human behavior is not as much a product of sheer genetics as some people would like to argue. I think there is just so much human behavior (homosexual behavior, for example) that is contrary to genetic fitness for the Dawkins explanation of human beings as DNA-replicating machines to be the whole story.

  3. Everyday Thomist on

    […] The word was coined by positive psychologist Jonathan Haidt, who I have written about here.   Haidt describes elation as that strong motivational tendency towards moral improvement that […]


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