Einstein admits he "knew nothing"

From Heisenberg, Physics and Beyond, Arnold J. Pomerans, trans. (New York: Harper, 1971), p. 63.

Heisenberg: "We cannot observe electron orbits inside the atom...Now, since a good theory must be based on directly observable magnitudes, I thought it more fitting to restrict myself to these, treating them, as it were, as representatives of the electron orbits."

"But you don't seriously believe," Einstein protested, "that none but observable magnitudes must go into a physical theory?"

"Isn't that precisely what you have done with relativity?" I asked in some surprise...

"Possibly I did use this kind of reasoning," Einstein admitted, "but it is nonsense all the same....In reality the very opposite happens. It is the theory which decides what we can observe."

Even geniuses cock up sometimes. This endorses everything I will achieve for the rest of my life ;)