  Though Reid identifies his target as having ancient origins, his primary concern is with what he regards as its modern equivalent. This modern theory was introduced by Locke and, according to Reid, extended to its inevitable idealist and skeptical conclusions by Berkeley and Hume. Reid excerpts passages from Locke’s Essay Concerning Human Understanding to illustrate the misleading metaphors Locke inherits from the ancient theory—metaphors of the mind as a storehouse and of ideas and impressions as pictures.