In this important and challenging book, Wolfgang Koehler's subject is value, or what he calls the requiredness of an object or activity. Starting with a descriptive account of values as we become aware of them, he finds that, inside certain contexts, parts of such structures do not appear as indifferent facts. They are experienced as belonging there intrinsically or, also, as being out of place in their contexts.

Koehler's closely reasoned analysis, drawing on the fields of psychology, biology, and physics, centers around this concept of requiredness. Certain things in nature belong together or require the presence of one another in such a way that fitness or requiredness constitutes a principles of association between them. This same principle of association, Koehler suggests, may help to explain the idea of value and lay a foundation for the scientific solution of ethical problems.