But after Newton, Einstein, Darwin and others, less of the physical world is left unexplained. Rather than a shortage, there is a plethora of theories to account, with apparent scientific precision and respectability, for whatever the average mortal does not understand.
In such a world, creatures such as the Loch Ness monster represent a nostalgia for the good old days when we knew less. Crop circles, unidentified flying objects, visiting aliens - all have their devotees, and all satisfy the need to react against rationalism.
But it is not only physical freaks of nature that serve this purpose. The assassination of John F Kennedy has been a gift to obsessives and supernaturalists, most recently and spectacularly the American film director Oliver Stone.
Similarly, some people believe that one of the figures on the cover of the celebrated Abbey Road album was in fact a tailor's dummy disguising the absence of a kidnapped Beatle.
Neither of these, however, could stand comparison with the great Elvis Presley question. For years after the singer's reported death, a US supermarket tabloid called the Weekly World News reported bizarre sightings of him, working in unexpected occupations in the southern states of the US.
It was a moment of great sadness when the paper finally published an exclusive eyewitness account of his 'real' funeral. Could that report be trusted, though? Might it not be that Elvis is at this very moment in a wetsuit, several hundred feet below the surface of Loch Ness, gurgling 'Blue Suede Shoes' to a guitar accompaniment provided by a scaly green creature?