Kant's theory of judgment establishes the conceptual framework for understanding the subtle relationships between the experimental scientist, the modern instrument, and nature's atomic particles. The principle of purposiveness which governs judgment has also a role in implicitly guiding modern experimental science. In Part 1 we explore Kant's philosophy of science as he shows how knowledge of material nature and unobservable entities is possible. In Part 2 we examine the way in which Kant's treatment of judgment, with its operating principle of (...) purposiveness, enters into his critical project and underlies the possibility of rational science. In Part 3 we show that the centrality given to judgment in Kant's conception of science provides philosophical insight into the investigation of atomic substances in modern chemistry. (shrink)