From antiquity the order of Philosophy (and the assorted 'sophists' which originally were not less prestigious than the other thinkers) dealt primarily with knowledge, man's viewpoint and the effect of the limits of it, studies of how a 'good' life can be had (eg ethics, temperance etc), physics (Artistotle wrote much later than Thales or even Anaxagoras), link between math and human logic, and many more specific thematologies.
After Aristotle there were more standard or noteworthy distinctions, primarily the one between physical and abstract philosophy (the latter termed 'metaphysical', but that was not meaning anything more than the book being the one after the Physics).
Christian philosophy for the longest time was theologic-centered (surprise). While Plato and Aristotle still were very significant, i have to suppose that the array of themes was quite limited (haven't really read much of christian philosophy, not even the Byzantine thinkers like Plethon Gemistos).
Descartes wrote some treatises on philosophy, meaning it as a new order along with his other innovations (cartesian axis etc). He also was dealing with other thematologies, such as medicine (iirc he had a false account of what role the heart plays in the human body?).
Philosophy seems to have taken a pretty sociological/political tone in England, due to most of the early (and probably more known) works of it there being politically themed, like the Leviathan and Utopia and other books which kill the reader by boredom
(i still recall that i had to read som chapters of Leviathan..).
Probably the most detrimental figure for the popular concept of what Philosophy is, was a rather intelligent german who served briefly in the Franco-Prussian war. Nietzsche was not in reality a philosopher, but mostly a theorist of the genealogy of ethics. Most of the rest of his work is a polemic against Idealism, but it is striking that he managed to see so little in what he refers to by that term. At times it appears he can barely differentiate between Idealism and Religious faith in a seperate world or realm.
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In my view the order of Philosophy, while being of ill-repute by now (as it deserves, sadly), is clearly distinct from sociology, economic theory, religious critique, political treatise or other largely practical knowledge or examination. Heidegger had noted that the rest of Philosophy has been only a note on the works of it during Antiquity. I think that the most clear core of that order is tied to the examination of what makes a human distinct both from his environment, and his own deeper and not conscious mental existence.
