Abstract
Certain philosophers have held the thesis of the unity of science. As often conceived, the thesis has two parts: the thesis of physicalism and the thesis of extensionality. For each of these two parts there is an outstanding problem, i.e. the problem of intentionality and the problem of intensionality respectively. The purpose of this paper is twofold: first, to make explicit the nature of these two problems, and second, to show to what extent they can be said to be the same problem. Thus I am not at all interested here either to defend or attack this thesis or either of its parts.