It really comes down to parsimony, economy of explanation. It is possible that your car engine is driven by psychokinetic energy, but if it looks like a petrol engine, smells like a petrol engine and performs exactly as well as a petrol engine, the sensible working hypothesis is that it is a petrol engine.
"Science, Delusion and the Appetite for Wonder". The Richard Dimbleby Lecture, BBC1 Television, 1996.
