Hume praises how ideas are always clear in mathematics. The problem with the science of morals, or moral philosophy, is “the obscurity of ideas and ambiguity of the terms” (44). Any idea of the mind is a copy of an impression that was experienced in the past, and this necessarily informs how our ideas are formed and connected. When one first encounters an object in the outside world, one can’t know the possible effect it will have; with experience, however, one can begin to infer the impact that tends to follow the prior action.

Philosophers discover that “even in the most familiar events, the energy of the cause is as unintelligible as in the most unusual” (51). Some philosophers are astute enough to recognize that power doesn’t lie in the human will. However, they naively assert God directly enacts this power: “Thus, according to these philosophers, every thing is full of God” (52), and in this manner, the laws of nature are overthrown. In truth, all that is revealed is their own ignorance.

In the second part of the chapter, Hume draws out the concept of moving from perceived conjunction to real connection.