Defense of Rationality?

Various forms of relativism, sometimes under the label of "postmodernism", have attacked the idea of rationlaity as such. Rationality is supposed to be essentially oppressive, hegemonic, culturally relative, etc. ... I am as appalled as anyone by these attacks, but I do not bother to answer them because I do not believe they can even be made intelligible. For example, I have sometimes been challenged, "What is your argument for rationality"--a nonsensical challenge, because the notion of "argument" presupposes standard of rationality. This book is not a defense of rationality, because the idea of a "defense" in the form of argument, reasons. presupposes constraints of rationality, and hence the demand for such a defense is nonsensical. ... One can intelligibly debate theories of rationality, but not rationality.

(John Searle, Rationality in Action, xiii-xiv)