There are different interpretations of the problem of universals. I understand it as the problem of giving the truthmakers of propositions to the effect that a certain particular is such and such, e.g. propositions like 'this rose is red'. Others have interpreted it as a problem about the ontological commitments of such propositions or a problem about what those propositions mean.

When I was eleven or twelve years old, I became for a while fixated on the question whether there could be two 'identical' stones. This is, of course, the question whether the principle of identity of indiscernibles is true and, as I formulated it then, I was bound to fall into confusion about it.

At one point I took a copy of Berkeley's Principles from my father's library. That was the first philosophy book I read. I found it fascinating and wanted to read more philosophy.

Knowledge has the form of a tree, and since metaphysics is the most fundamental one of the theoretical disciplines, it represents the roots of the tree.

Although I felt I was quite good at criticising a philosophical position, I was not very good at defending and making a case for a philosophical position.

Leibniz believed in freedom, both divine and human, and he thought that contingency was a necessary condition of freedom. That is, if an agent A acts freely when choosing X, then A's choosing X cannot be necessary. But there are some elements in his philosophy that seem to make contingency impossible.

I think there is a metaphysical problem of the relation between mind and body. Thinking that there is no metaphysical dimension to the problem is an error.