Abstract

A natural reading of Hume’s distinction between impressions and ideas is that impressions are forceful perceptions whereas ideas are faint. A problem emerges, however, when Hume countenances the possibility of faint impressions and forceful ideas. In this paper, I attempt a resolution to the problem. I argue that Hume characterizes impressions and ideas intensionally and extensionally, and sometimes uses the term in only one of the two senses. I argue that Hume intensionally defines impressions and ideas as forceful perceptions and weak perceptions, respectively, but takes these to be extensionally equivalent to original and copied perceptions, respectively. Hume recognizes that his two characterizations—the intensional and extensional—don’t perfectly match up, and that there are exceptions to the purported equivalences (the exceptions being disease, sleep, madness, and enthusiasm). Nonetheless, I argue that Hume’s willing to proceed with his definitions.