A physicist visits a colleague and notices a horseshoe hanging on the wall above the entrance. 'Do you really believe that a horseshoe brings luck?' he asks. 'No,' replies the colleague, 'but I've been told that it works even if you don't believe in it.'
A visitor to Niels Bohr's country cottage, noticing a horseshoe hanging on the wall, teasing the eminent scientist about this ancient superstition. "Can it be true that you, of all people, believe it will bring you luck?' 'Of course not,' replied Bohr, 'but I understand it brings you luck whether you believe it or not.'
Of course I don't believe in it [pointing to horseshoe on his office wall]. But I understand that it brings you luck whether you believe in it or not.
