Philosophy Prof Argues Human Nature Doesn't Exist. Commits Logical Fallacy

Michael Liccione | December 21, 2017

Philosophy Prof Argues Human Nature Doesn't Exist. Commits Logical Fallacy

In this new article for Aeon, Ronnie de Sousa, professor emeritus of philosophy at the University of Toronto, argues that the facts of evolution entail that “there is no such thing as human nature.” Instead, what we are is what we make of ourselves by our individual and collective choices. There is no prior “human nature” to which our choices ought to conform. As the great existentialist Jean-Paul Sartre put it, human “existence precedes essence.”

Thanks more to postmodernism than to existentialism, that view is rather fashionable these days. But is it true?

I don’t believe so. To show why, I shall expose and rebut the key fallacy in de Sousa’s argument.

In the first third of his piece, de Sousa notes the difficulty of answering the question what human beings ought to value (i.e., see as good), and accordingly pursue. The key problem is the well-known “naturalistic fallacy”: the attempt to derive what ought to be the case simply from what is the case, especially in Nature.

In de Sousa’s view, St. Thomas Aquinas (1225-1274) made the best attempt to get around the naturalistic fallacy by devising “an ingenious two-step strategy for answering that question”:

“Step one: look at what happens ‘always or for the most part’ in nature to determine its laws. That investigation will reveal the natural and proper ‘functions’ of organs and activities: those that Nature, so to speak, ‘intended’. (If Nature is just another name for God, then the talk of ‘intent’ can even be taken literally.) Step two: use the resulting observations to determine what we ought to do – and especially what we ought not to do – according to whether it was found to be ‘natural’ or ‘unnatural’ in step one.”

In that grossly oversimplified summary, de Sousa purports to find a problem in Aquinas’ justification of natural law:

“Unfortunately, Aquinas’ strategy, though still holding sway in the Vatican as the doctrine of natural law, is a slippery example of ‘bait-and-switch’. In step one, the word ‘law’ seems to be used as in science, to refer to descriptive generalisations about what actually happens. In step two, however, the word’s meaning is closer to that of ‘legislation’. Laws of this second sort are promulgated and often broken. Laws of the first sort cannot be broken, even if they are stochastic, specifying mere probabilities. Laws of one kind are about the facts of nature; laws of the other kind are about how we should change those facts.” 

He goes on to argue that such reasoning seemed plausible enough before Darwin, but no longer holds now that the origin of species by natural selection of genetic mutations has been so well confirmed.

I’ll get to that claim in a moment. Here I note that de Sousa’s critique of “natural law” as a moral theory hinges on a fallacy of equivocation.

The equivocation is on the term “nature”. De Sousa criticizes Aquinas for deriving the prescriptions of “the natural law” for what we ought to do from descriptions about Nature, with God filling in the gap between the two. If that’s what Aquinas did, it would be a pretty obvious instance of the naturalistic fallacy. But it wasn’t.

When Aquinas spoke of human nature, he was speaking about something more, and more important, than what we find in Nature. In his view (which is not just his view), a live human being has a “rational soul” that is non-material and thus cannot be produced by Nature alone. We can learn about it from the fact that our thoughts and choices are not reducible to their material realizations. The distinctive faculties of the human soul, intellect and free will, are therefore capable of thoughts, choices, and actions that are not derivable from Nature alone. Such are the considerations that are distinctively human. They provide reasons for action that cannot be learned just from observing Nature, though Nature of course sets important limits on what is physically possible as well as providing clues and analogies. It is precisely from such considerations that the precepts of the natural moral law are derived.

But de Sousa never engages that distinction. He simply conflates a modern sense of the term “nature” with Aquinas’ more metaphysical usage—a fallacy of equivocation.

Of course he is quite right to argue, as he does in the rest of his piece, that we cannot learn what we ought to do just from what we learn about ourselves from evolutionary biology. In a backhanded way, de Sousa even acknowledges that Nature alone does not set the horizon for our (rational or irrational) thoughts and desires. From a standpoint strictly limited to what Nature supplies, there is accordingly no fixed limit to what it’s “natural” for us to want and do.

But it doesn’t follow from this that there’s no human nature in the sense typically assumed in natural-law ethics and discernible from basic, distinctively human goods such as knowledge, friendship, and marriage. That’s an issue de Sousa hasn’t really addressed. 



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