As conscious beings, we exist only in response to other things, and we cannot know ourselves at all without knowing them. Moreover, there is nothing in theory, and certainly nothing in experience, to support the extraordinary judgment that it is the truth about himself that is the easiest for a person to know. Facts about ourselves are not peculiarly solid and resistant to skeptical dissolution. Our natures are, indeed, elusively insubstantial — notoriously less stable and less inherent than the natures of other things. And insofar as this is the case, sincerity itself is bullshit. [italics mine]
So much for Shakespeare's injunction "to thine own self be true." Actually, come to think of it, Shakespeare was wiser than we usually recognize. He put that injunction in the mouth of a pompous fool who would soon die as a result of misunderstanding. Hmmmmm, gotta think about that.