Principles of Ethics by Antonio Rosmini

Because human beings are cognitive and active, human life is concerned with theory and practice. The same cannot be said, strictly speaking, about philosophy which is never action but always consideration, whatever the subject under consideration. Philosophy is entirely and essentially theoretical. Nevertheless, because it deals with action or practice we have become accustomed to speaking about practical philosophy instead of the theory of practice. This kind of linguistic shorthand, however, is dangerous. It would be far better — and it is extremely important, generally speaking — to use a longer, more exact phrase, which safeguards the genuine meaning of words, than to lay ourselves open to error by preferring misleading brevity to clarity. We shall not follow the usual practice therefore of separating theoretical from practical philosophy, but consider philosophy as two theories, one concerned with how beings exist and act, and the other with ourselves and the way in which we have to act.