None of these men, it is to be noted, tried to answer these questions [about the nature of the universe] by an appeal to any revelation, to myth, or religious knowledge of any kind; but attempted to extract the answer by using their reason; and they used it almost without reference to sensible observation and experiments. Why was this ? Clearly because they were convinced that the thing they sought lay deeper in the heart of the world than the superficial aspect of things, of which alone the senses could tell them. They were seeking the underlying causes of things, and this is the special point of view from which philosophy discusses its multifarious objects, which are dealt with from another aspect, by special sciences, such as chemistry, biology, zoology, and so on. It intends to go further into their nature than these do, and not to rest content until it has uncovered the absolutely fundamental reasons of them all [my emphasis].Thus we define philosophy: the attempt to uncover the fundamental reason of everything, without (like religion) appealing to revelation, myth or other forms of authority, but without (like natural science) the use of observation of experiment. Approaching the world by pure unaided reason.
Also just out in the Logic Museum, the commentary on Aristotle's Metaphysics by Albertus Magnus. I have corrected the scan up to book I tract 3, the rest is a bit of a mess. And of course it is only in Latin. Tract 3 is Aristotle's own account of the history of philosophy before him.