Having distinguished between metaphysics and theology, we can now deal with philosophy in general. More specifically, we have in mind philosophy as it stands today and in recent centuries, since it became separated from any traditional framework. This ‘philosophy’ is of course quite a different animal from the teachings of Plato, and although what we say will have some correspondence with the philosophy even in its early Greek form, our criticisms will apply less to the ancient schools than to what, today, passes for philosophical thought.
Philosophy, as we encounter it today, is composed of so many heterogeneous elements, with lines of demarcation so unclear, that it is no exaggeration to say that the unity of philosophy is mostly imaginary, and that much like contemporary thought in general, its meaning is dictated more by sentiment than by reasoned criteria. We might say that its unity is mostly ‘historical’, since there has been, since its birth with the Greeks, a body of knowledge that goes by this name. Beyond that, all we can really say of the ‘sciences’ that compose what is today called philosophy is that they are the work of human reason; and with the exception of logic, we can add that they all more or less claim to be based on observation and experimentation. In other words, they have a unity of method. This tenuous unity, which we might call ‘rational inquiry’, is enough to show that philosophical knowledge is, regardless of its ‘area of study’ or emphasis, of an order separate from and below metaphysics.
The knowledge proper to metaphysics is not only beyond observation, but also, as we have explained, beyond the reach of discursive thought. Having made this initial distinction, which helps us to keep philosophical knowledge in its proper place, we can proceed through the philosophical sciences, as they are conventionally grouped, observing their character from the point of view our study entails.