Now that we know what the object studied by philosophy is, it's not hard to see that this object, by its very nature, will be quite complex. This is so because states of consciousness involve quite diverse types of phenomena. In order to study them all, we'll have to divide the science of philosophy into several specific sciences.

Different philosophical systems have proposed different ways of dividing philosophy, and this is entirely natural, for these divisions are tied to the general spirit of the system in question. In the earliest days of Greek thought, philosophy wasn't divided. It was said to be the whole of human knowledge. Philosophy was thus confused with physics and, until Socrates came along, all philosophical treatises bore the title: Περìϕύως (On Nature). We don't know if Socrates divided philosophy or how he divided it. Plato, who more than anyone else made Socrates' philosophy known to posterity, didn't divide it. So it's unlikely Socrates himself did. For Plato, philosophy is synthetic. Rather than discussing a distinct part of his system, each dialogue touches on many different questions, which seem to be only randomly connected.

Aristotle, who saw philosophy as comprising quite different sciences, was the first to divide it neatly: “All human activity,” he said, “can take three different forms – knowing, acting, doing. From this we get three sciences: theory, whose object is speculation; practice, which is equivalent to what we today call ethics; and finally, poetics, whose object is art.”