We can philosophize about life, the universe, gods, or society, about physics, religion, art, literature, or war, about politics, economy, or paradoxes, about moral, ethics, aesthetics, consciousness, math, language, science, pets, love, sex, fashion, travel, murder, the weather, loogic, argument, astrology, dreams, or the mind, reality, truth, and maybe even about an orange carrot.
It seems clear that knowledge about the subject one philosophizes about is an a priori for philosophizing. Or does philosophy contribute to that knowledge? Is the subject philosophized about part of philosophy, like logic, argument, or ethics maybe? Is there a difference between parts of philosophy and philosophizing about these?
What's does philosophy say about the nature of philosophy itself?
In other words, is there something like pure philosophy, without applying it to a subject, like there is pure mathematics without applying it to physics? Is math maybe pure philosophy?
I still other words, what's left of philosophy if the subject philosophized about is left out? Is there a set of philosophy rules that can be applied to an arbitrary subject, like there are mathematical rules that can be applied to an arbitrary subject? Are there subjects to which philosophy doesn't or can't apply, like math can't be applied to all subjects?