  The most controversial application of this view is to mental phenomena. Within that realm, Quine focuses on attributions of propositional attitudes, statements that so-and-so believes that such-and-such, or hopes that, or fears that, etc. (One reason for this focus may be that his interest is primarily in human knowledge; another that some other mental states, such as pain, can perhaps be accounted for by identifying them with certain types of neurophysiological events.)