The course is given to an examination of the impact of molecular biological methods and concepts upon the biomedical sciences. Has molecular biology become just a bag of tricks with which to carry on "business as usual"? Have these sciences, perhaps, changed their outward appearance but not their hearts? Consider the neutral theory, the home box, jumping genes, or prions. We take examples like these and explore the nature of the concepts, the degree of discontinuity in their history, and the dependence of these changes on the molecular approach.