How to evaluate a philosophical theory

A handy-dandy guide to make sense of what philosophers say

Peter Adamson, co-inventor of the Adamson-Ganeri test for evaluating philosophical ideas. Image from whatisitliketobeaphilosopher.com.

I don’t know if you have come across the writings of my colleague Peter Adamson. I’ve recently made them the focus of a special edition of my occasional recommended readings. Peter is a professor of ancient and medieval philosophy at King’s College London and the host of a long running podcast entitled A History of Philosophy Without Any Gaps. He was also the 2021 keynote speaker at the annual World Philosophy Day event that I host at City College.

And yet, this post is not really about Peter! However, it is inspired by something he wrote at the beginning of chapter 39 of the book he co-authored with Jonardon Ganeri on classical Indian philosophy. Here is what they say:

“When you’re evaluating a philosophical theory, there are a few tests you should always carry out. Does the theory preserve our intuitions? If not, does it give us sufficient reason to prefer this new theory to our previously held beliefs? Does the theory fall prey to counterexamples or leave unexplained exceptions? And here is one more test that should never be omitted: can the theory survive being applied to itself?”

It’s an excellent guide to understanding philosophical claims, so I figured we could apply it to a couple of instances to begin to get the hang of it.

First, though, a caveat. While Adamson and Ganeri talk about “philosophical theories” I don’t particularly go for that term because it reminds people too closely of scientific theories, and I think there are major differences between the two, because science and philosophy—though continuous and mutually informing fields—are sufficiently different from each other that we shouldn’t mix up their respective methodologies.

Science works on the basis of theories that relate directly to empirical evidence. Scientific theories—say quantum mechanics, or the theory of evolution—arise in response to new evidence concerning natural phenomena, attempt to account for such evidence, and make predictions about new, as yet unobserved phenomena.

Philosophical “accounts”—my preferred term—do not depend directly on empirical evidence, though they ought not to be in contradiction with such evidence. And their aim is not to produce predictions about future observations, but rather to further a broad conceptual understanding of certain problems. Examples include accounts of ethical systems, such as virtue ethics, Kantian deontology, or utilitarianism; as well as accounts in philosophy of science, like Thomas Kuhn’s idea of paradigm shifts, or Karl Popper’s notion of the role of falsification in demarcating science from pseudoscience.