Can Metaphysics Be Naturalized? And If So, How?

I began to study philosophy about 30 years ago.1 It is clear to me, as it is to every philosopher who has lived through the intervening period, that the way in which philosophy is practiced today is very different from the way in which it was practiced then. The obvious outward sign of this difference in practice is the greatly increased probability that a philosophical journal article or book will discuss or cite the findings of some kind of empirical investigation, usually a science, but sometimes a branch of history. The difference itself is the (partial) so-called naturalization of many branches of philosophy. Reflection on the contemporary practice of, say, philosophy of mind, philosophy of science, philosophy of language, moral philosophy, and even political philosophy suggests that the findings of empirical investigation play two main roles when philosophy is naturalized. First, they serve as evidence intended to confirm or disconfirm philosophical theses, theses that may themselves be quite traditional. For example, such findings have recently been used to cast doubt on the traditional claim that we have infallible knowledge of our own current experiences; and other findings to support an approximately Humean sentimentalism about moral judgments.2 Second, such findings play the role of object of philosophical inquiry, in effect generating new philosophical questions. For example, the perplexing results of experiments performed on patients whose left and right cerebral hemispheres had been largely disconnected have generated much