III need some other type of evidence to draw conclusions about the mental states of others

 A 'mind' problem is often stated in terms of a contrast between the relatively secure way in which I “directly” know about the existence of my own mental states, and the far more epistemically risky way in which I must infer the existence of the mental states of others. 

Thus, although I can presume to know about my own mental states simply by introspection and self-directed reflection, because this way of finding out about mental states is peculiarly first-person, I need some other type of evidence to draw conclusions about the mental states .of others

 Thus the problem of other minds is chiefly an epistemological problem, sometimes expressed as a form of skepticism about the justification that we have for attributing mental states to others