 The plausibility of (4) may be appreciated as follows. Whatever else knowledge is, it is plausibly regarded as a species of true belief. A belief is an intrinsic state of a subject. Moreover, to unpack the second clause of (3), beliefs are individuated by their contents: beliefs or believings with different contents are different beliefs. It cannot be that one and the same act of believing has different contents at different times or in different possible worlds.