David Hume and the $20 bill on the sidewalk

 David Hume (1748) wrote in An Enquiry Concerning  Human Understanding: 


"A man who at noon leaves his purse full of gold on the pavement at Charing-Cross, may as well expect that it will fly away like a feather, as that he will find it untouched an hour after. Above one half of human reasonings contain inferences of a similar nature, attended with more or less degrees of certainty proportioned to our experience of the usual conduct of mankind in such particular situations."