Recent ‘revisionist’ studies of the Scientific Revolution have utilized Robert Hooke as an example of a mechanical philosopher who incorporated active principles in his world system. This paper carefully examines Hooke's natural philosophy in order to determine the extent to which he employed active agents in his work. Thorough investigation reveals that although Hooke sometimes refrained from offering causal explanations of the phenomena he studied, there is no solid evidence that he believed active principles were at work in nature. Rather, (...) his major tool for interpreting nature—his theory of congruity—follows wholly mechanical principles, as do his explanations of the essences of the fundamental constituents of the universe. Hooke emerges from this analysis as a purely mechanical philosopher. (shrink)