This book examines the various norms for the logic and methodology of science, placing them in the context of the cognitive interests and explanatory ideals that motivate science. Various themes in the philosophy of science are examined, including the views of K. Popper, T. Kuhn, and L. Laudan. Characteristic cases of scientific theories are examined in order to illustrate and justify the proposed norms. These include, on the one hand, the emergence of the science of Galileo, Kepler, and Newton from the older metaphysical style of explanation to be found in Aristotle and, on the other hand, Darwin's theory of natural selection.