 Hume doesn’t try to explain why we associate ideas as we do. He is interested only in establishing that, as a matter of fact, we do associate ideas in these ways. Given that his claim that the associative principles explain the important operations of the mind is an empirical one, he must admit, as he does in the first Enquiry, that he cannot prove conclusively that his list of associative principles is complete. Perhaps he has overlooked some additional principle. We are free to examine our own thoughts to determine whether resemblance, contiguity, and causation successfully explain them. The more instances the associative principles explain, the more assurance we have that Hume has identified the basic principles by which our minds work.