For knowing is spoken of in three ways: it may be either universal knowledge or knowledge proper to the matter in hand or actualising such knowledge; consequently three kinds of error also are possible.
[Misquotation; not by Einstein.] If only I had known, I should have become a watchmaker. [Apparently remorseful for his role in the development of the atom bomb.]
Man, being the servant and interpreter of Nature, can do and understand so much and so much only as he has observed in fact or thought of the course of nature; beyond this he neither knows anything nor can do anything.