 Hamilton argues that the age-old search for a philosophy of the unconditioned is futile, and he contends that what is in effect a combination of phenomenalism and presentationism will supply everything that a properly grounded understanding of reality requires. In “The Philosophy of Perception” he engages in the debate by defending Reid against criticisms in Thomas Brown's posthumously published Lectures, and in a very vigorous manner—“It is always unlucky to stumble on the threshold. The paragraph (Lect. xxvii) in which Dr Brown opens his attack on Reid contains more mistakes than sentences” (ibid. 69). Brown claimed that a close analysis of Reid's writings showed that his position on perception was not really that of direct realism but “hypothetical realism”, that is the belief in an external world that cannot be known directly. It is this contention that Hamilton aims to refute, but it is arguable that he misinterprets Brown. Moreover in his notes to Reid's Collected Works, which were composed rather later, he appears to come round to something very like Brown's interpretation and to hold that Reid was not, strictly speaking, a direct realist after all.