Here are two groups of Western philosophers. We’ll call them Group A and Group B. Here’s Group A:

Plato, Epicurus, Plotinus, Aquinas, Duns Scotus, Francis Bacon, Hobbes, Locke, Spinoza, Newton, Leibniz, David Hume, Herbert Spencer, John Stuart Mill, Schopenhauer, Kant, Kierkegaard, Nietzsche, Wittgenstein, Jean-Paul Sartre, Kurt Gödel, Karl Popper, Jeremy Bentham, Alan Turing, Saul Kripke.

And here’s Group B:

Aristotle, Socrates, Descartes, Bishop George Berkeley, Rousseau, Heidegger, Hegel, Marx, Frege, Bertrand Russell, John Dewey, Albert Camus, Frantz Fanon, John Rawls, Willard Quine.

Okay, so: what distinguishes these two groups?

Answer under the cut, but… stare at those two lists. Take a moment; give it a try. Do you see it?

Hints: It’s something pretty straightforward. Frege is an edge case. And while Rousseau is formally part of Group B, he really belongs with Group A.

If you have a guess, put it in a comment, then come and look. [click to continue…]