The good, we are told, is happiness, which is an activity of the soul.
 Bertrand Russell, A History of Western Philosophy (1945). copy citation

Context

“The book appeals to the respectable middle-aged, and has been used by them, especially since the seventeenth century, to repress the ardours and enthusiasms of the young. But to a man with any depth of feeling it cannot but be repulsive. The good, we are told, is happiness, which is an activity of the soul. Aristotle says that Plato was right in dividing the soul into two parts, one rational, the other irrational. The irrational part itself he divides into the vegetative (which is found even in plants)” source