Ben Graham’s concept of “Mr. Market” (by Charlie Munger)

“Ben Graham had his concept of ‘Mr. Market.’ Instead of thinking the market was efficient, he treated it as a manic-depressive who comes by every day. And some days he says, ‘I’ll sell you some of my interest for way less than you think it’s worth.’ And other days Mr. Market comes by and says, ‘I’ll buy your interest at a price that’s way higher than you think it’s worth.”

~ from the book, Charlie Munger, The Complete Investor