Louis Bachelier

Past, present, and even discounted future events are (all) reflected in market price.

[Note: Louis Bachelier wrote this in his Ph.D. thesis at the Sorbonne in 1900. Nearly half a century later, when Nobel Laureate Paul Samuelson discovered the long-forgotten thesis, he confessed that he "oscillated . . . between regarding it as trivially obvious (and almost trivially vacuous), and regarding it as remarkably sweeping."]