 More broadly, however, Mill’s theoretical view of mind and world is as a whole circular and self-supporting. Mill’s naturalistic picture of the relation between mind and world—of the mind as itself part of the natural order and incapable of knowledge a priori—must itself be treated as a substantive discovery. As such, it could only be arrived at by inductive reasoning. Inductive investigation allows us to better understand that the mind is itself governed by natural laws—and to better understand the processes of sense perception that allow us to be causally receptive to the world. Elements of Mill’s associationist psychology are apt to strike us as outdated—but that does not alter the basic point that the naturalistic study of mind has been enormously successful in affording a better understanding of how we process the world we occupy. Such discoveries clarify and strengthen our sense of why a priori knowledge is impossible in the first place, and why empirical investigation is necessary for any genuine knowledge.