In the writings of such "pagan" philosophers as Plutarch and Porphyry we find a humanitarian ethic of the most exalted kind, which, after undergoing a long repression during medieval churchdom, reappeared, albeit but weakly and fitfully at first, in the literature of the Renaissance, to be traced more definitely in the eighteenth century school of "sensibility." But it was not until after the age of Rousseau, from which must be dated the great humanitarian movement of the past century, that Vegetarianism began to assert itself as a system, a reasoned plea for the disuse of flesh-food.