It would surely be a gross understatement to say that the vocabulary of rationality has become problematized in the philosophical situation of our time. Admittedly, the question "What does it mean to be rational?" has been asked by the learned and the vulgar alike for some time; and it has been taken for granted that philosophers, both by disposition and training, are those best equipped to answer the question. Indeed, it could well be said that in the tradition the question "What does it mean to be rational?" has been indissolubly linked with the question "What does it mean to be a philosopher?" To do philosophy, it has been assumed, is to put into play, in a variety of ways, the claims of reason; and to be a philosopher is to take on the mantle of the guardianship of rationality.