We talk a lot about thinking, but rarely think about what thinking really is. René Descartes, a 17th century French philosopher, thought he had brought the subject to a close with his conclusion that, “I think, therefore I am.” But his position was countered by the 18th century French philosopher, Jean-Jacques Rousseau, who contended that,“I feel, therefore I am.” But all this speculation was centuries ago, without either having access to the wealth of neurological and cognitive evidence available in the 21st century.