Philosophers often find it useful to classify theories bearing upon a problem according to some typological scheme. In Five Types of Ethical Theory, C. D. Broad treats Spinoza, Butler, Hume, Kant, and Sidgwick not only as moral theorists but also as examples of basic approaches to the subject. In a final chapter Broad includes these and other theories, actual and possible, in a comprehensive classificatory scheme. Similarly Ogden, Richards, and Wood, in The Foundations of Aesthetics, advance a schematic outline of the principal approaches to aesthetics. Why such schemes are helpful is not hard to see. For one thing, they bring order to the otherwise unmanageable number of theories in fields such as ethics and aesthetics. In order to be useful, however, classification must also be accurate, and this means that a good typology of theories embodies a good deal of analysis. Before one says that two or more theories are fundamentally-not just apparently-similar or different in this or that respect, one must have penetrated to the base of the theory, to its generative premises and assumptions. One must also know intimately how the theory gets from these to its conclusions and applications, so as not to be misled by the latter. This analytical work, as well as the classification scheme which is its completion, are helpful, finally, in the criticism and evaluation of the theories themselves, thus preparing the way for new theoretical work.