Cohen's most important book, Reason and Nature:

An Essay on the Meaning of Scientific Method was first published in 1931 and rapidly became a classic. A second edition appeared in 1953 (cover seen here) due to the efforts of Felix Cohen. In this work, Cohen stresses the role of reason and the importance of theory. Cohen warns against putting too much emphasis on the inductive stages of a science that merely add facts, with the central characteristic of the process the deductive elaboration of hypotheses. Cohen is aware of the explicit consciousness of the polarity of ideas in their application to nature, Insisting that "we keep our categories clean," while recognizing their joint applications, and at the same time, one can recognize continuities without being committed to reductionism.

The work is divided into three parts. The first part analyzes reason in relation to the scientific method. The second part examines the nature of mathematics and its application to the material world, progressing through central philosophical problems in physics, biology, and psychology. The third part is a collection of essays concerning the relationship of the social sciences to the natural sciences. Cohen deals with the perennial issues required by a balanced approach in the growth of knowledge. Cohen acknowledges that such a balanced approach is necessary for the continued success of each inquiry. On a larger scale, he is also exhibiting the mutual need for the co-operation of philosophy and the sciences in illuminating man's world.