I don’t reckon it is. Specifically, his moral theory and the infamous categorical imperative. Here’s why.
Any individual who strictly adheres to Kant’s moral theory would be at a selective disadvantage to one who didn’t. Or, if you’re fond of group selection (or multi-level selection, or whatever supra-individual selection), any group that strictly adheres to Kant’s moral theory would be at a selective disadvantage to a group that didn’t.
This means that over multiple generations, Kant’s moral theory – regardless of whether it’s inherited via genes or memes – would eventually give way to another moral system that lent a greater selective advantage.
Game theory can be used to demonstrate this point. The only way to apply the categorical imperative to a game like the prisoner’s dilemma is think of the imperative as a general strategy, such as:
Choose only a strategy which, if you could will it to be chosen by all the players, would yield a better outcome from your point of view than any other.
This would result in you always choosing to cooperate. And as we know from the many iterated prisoner’s dilemma experiments, a Nice strategy like this gets thoroughly trounced by Nasty, or even more balanced strategies like Tit for Tat. So, should the Prisoner’s Dilemma (or other games) reflect reality and your chances of survival, then choosing a Kantian morality puts you at a significant selective disadvantage.
This can also be called the Fallacy of Enlightenment – a fallacy that I reckon riddles much of moral philosophy from the last two and half thousand years. It goes a little something like this: ‘if everyone was just nice to each other, we wouldn’t need laws.’
While this statement is true, it’s a terrible basis for a moral system. For such a system would be vulnerable to those individuals who weren’t nice, who could exploit the nice ones for their own advantage. And the world is a Nasty place; give an inch, and natural selection will make it a mile. So, no moral system that can be paraphrased as the Fallacy of Enlightenment – such as Kant’s – is compatible with evolution.
So let’s stop talking about moral theories that would be eliminated by natural selection in a handful of generations as if they were fair game. From here on in, if a moral system lends a selective disadvantage, let’s treat it as a test tube case, not as a viable real world option.