The famous physicist Neils Bohr, pioneer of the Standard Model of Quantum Physics once had a visit from an Italian physicist to his office. Upon seeing a horseshoe pinned above Bohr's office door, the Italian remarked;

'Surely you, a man of science, do not believe in such things!'

To which Bohr replied;

'Of course not, but I understand you don't have to believe in it for it to work.'