Reflexivity: The ‘Essence’ of Philosophy?

Positing that any one idea, aim, method or habit is the essence of philosophy will never be a popular move. Philosophers are particularly capable of pointing out the exceptions to the rule, and resisting generalisations. But one of the more promising suggestions I have heard which I am currently entertaining is that reflexivity is the essence of philosophy. The dictionary on my Mac defines this as:

Re.flex.ive. GRAMMAR. Denoting a pronoun that refers back to the subject of the clause in which it is used, e.g., myself, themselves.

To take the normative realm as an example, philosophy asks questions about whether a certain knowledge claim is justifiable, whether a method of thinking is reasonable, and whether certain acts are right and good, without having immediately deployable conceptions of exactly what it would take for a knowledge claim to be justifiable, or what it would take for a method of thinking to be reasonable, or what it would take for certain acts to be good or right. I’ve come across this idea most strongly in Immanuel Kant, who embarked on a Critique of Pure Reason, and encourage others to join him, without explicitly setting up what it would be to constitute ‘reason’, instead taking off down the path of critique and amending definitions, aims and methods along the way through a process of clarification and analysis of new findings.

Perhaps this is one reason for the antagonism between a discipline like theology and philosophy. Philosophy is more inclined to leave a lot of premises, methods, ascriptions and categories open and fluid, and to proceed down a dark and foggy path of clarification and self-scrutiny, whereas much theology is written with strong claims about objectivity and value in place – that is, it has a good idea of what it thinks it would take for something to be justifiable, reasonable, good, right etc. For theology to be continually pulled back to these abstract and foundational categories can be frustrating.

What do you think about this view? Do you think this is a significant source of friction between the two disciplines?