  Hume is less interested in affirming ontologies than in showing why we have no good reason to invest belief in them, and accordingly picks up on the rather different Gassendist theme of coming to terms with the ancient Skeptics. His moderate or constructive skepticism (pace Popkin) is founded on doubts concerning the possibility of justified belief, focusing on the problem of induction as the great difficulty undercutting our ability to know about the world. Lacking rational justification, we simply fall back on induction as a practicable means of grasping and managing our experience of events. Here we see a striking similarity with Gassendi's assessment—beginning with the observation that justifying any generalization on particulars requires something beyond our cognitive powers, namely, our empirical knowledge of all such particulars. From this point, Hume draws the Gassendist lesson that induction cannot be demonstrative, for lack of this generalization step or the supposition “that apart from those enumerated there occurs none which is different” (O I (Institutio Logica) 113a). Finally, Hume's proposed resolution also resembles Gassendi's notion that we might simply posit, as a matter of utility, the conformity of all remaining unenumerated particulars.