I contend that philosophy in all of its facets is one integrated discipline. And they in turn are held accountable to, and hold up to account, the philosophy of culture. Therefore, I understand philosophy to be a systematic discipline, not a set of relatively unrelated subdisciplines. To do philosophy well, one must work in many areas of philosophy. Any philosophical conclusion is tested partly by how well its implications work out throughout the discipline.
Rational inquiry comes in many forms.
In philosophy reason proceeds in an unusual, indirect manner. The problem is that we can approach philosophy's goal only obliquely. And since we best grasp and analyze our thinking through the language that reports and expresses thought, we look to how we speak, and to what it does and does not make sense to say, about some subject, in order to tell us how we think about that subject. Philosophy therefore works by means of a rigorous analysis of language. We reason from how we do think to how we must think.