“However, the pursuit of self-awareness breaks down if we try to extend this kind of external psychological criticism of ourselves to the limit—which must happen if we entertain the possibility that nothing in human thought really qualifies as reason in the strong sense I wish to defend. For we are then supposed to consider the completely general possibility that there are contingent and local explanations of the sources of all our convictions, explanations that do not provide justifications as strong as reason would provide, if there were such a thing. And the question is, what kind of thought is this? It purports to be a view of ourselves from the outside, as creatures subject to various psychological influences and prey to certain habits, but what are we supposed to be relying on in ourselves to form that view?”
Taken from The Last Word (2001) by Thomas Nagel.