"I am wont to think that men are not so much the keepers of herds as herds are the keepers of men, the former are so much the freer. Men and oxen exchange work; but if we consider necessary work only, the oxen will be seen to have greatly the advantage, their farm is so much the larger. Man does some of his part of the exchange work in his six weeks of haying, and it is no boy's play. Certainly no nation that lived simply in all respects, that is, no nation of philosophers, would commit so great a blunder as to use the labor of animals."
(Henry David Thoreau. Walden )