 Hartley’s starting point is the living organism, and specifically the physical “vibrations” present in brain and nervous system and in the universe with which the organism interacts. From this starting point, two important considerations follow. The first is that sensations and ideas are products, not givens, and their “generation” and “raising” require explanation. The second involves the recognition that organisms are active beings. Like other animals, humans move about in, explore, and interact with their environments. What is more, humans become adept at performing various kinds of learned, highly skilled actions—e.g., playing the violin. The “ideas” humans have largely occur within, and guide, such practices.