The philosophy I studied in college was not a 'historical study of great men' or any sort of literary study. It was study of the ideas, with the various works (usually short works, not big things but excerpts and such) used as clear explanations of them. And then study of what responses were made to those, what their merits were, what the flaws or strengths of the idea are, etc.
And philosophers DO consult the original sources. Those would be basic logic and rhetoric. Then they take those and they first build epistemology. Then they use that epistemology to build a framework of metaphysics. Eventually they build the most abstract, highest level piece - ethics. At each step there are varying options, and it is rare that you can point to any of the options as 'clearly true'.
We already know mathematics and similar cannot address everything. A 3-body system of perfect sphere interacting solely under universal gravitation is already in itself so sensitive to initial conditions that the error on any prediction you make grows faster than anything computable. So how is humanity to deal with things that happen on the scale of trillions of trillions of entities interacting in non-linear ways constantly? That's the world we actually live in, and the tools to address it won't come from math. And probably not physics (although maybe).