“Every century has its own spirit; that of ours seems to be liberty.” So in 1776, when men were beginning to say that it was time to burn philosophers instead of their books, and a boy of eighteen was actually burned, Diderot wrote to Voltaire, in the famous letter in which he announced that in spite of all he would stay in Paris, among the enemies of liberty, to carry on his own mission. Timidity in political matters was excusable in Diderot’s day, and existed even among the men of his own set. Helvetius, for instance, advocated the advantages of paternal government and benevolent despotism; with his usual keen and vigorous good sense, Diderot shows how unreal these advantages are. When we give a ruler absolute power to do good, we cannot prevent him assuming also an absolute power to do evil. Moreover, as Diderot insisted, it is not possible to make people good against their wills, nor is it desirable to treat men like sheep. “If they say, ‘We are well enough here,’ or if, even, they say, ‘We are not well here, but we will stay,’ let us try to enlighten them, to undeceive them, to bring them to saner views by persuasion, but never by force.” “The arbitrary government of a just and enlightened prince is always bad.” He insists, again and again, that we must never let our pretended masters do good to us against our wills. “Whenever you see the sovereign authority in a country extending beyond the region of police, you may say that that country is badly governed.” Diderot, Goethe, Adam Smith, Beccaria, Mill, to mention but a few typical names, threw all the weight of their influence, sometimes with passionate emphasis, on the side of individuality and freedom, and their teaching reached its final consecration when Darwin accepted as his central theory the fruitful idea of Malthus. They felt, and rightly felt, that they were taking the step that was most needed. Those who advocated solidarity and social co-operation mostly went to the wall. Now it is the turn of the social instincts, and we must expect them to work themselves out to the utmost. We have to see to it that the truth to which Diderot and the rest fought their way is not meanwhile lost. The general will is itself to-day in danger of becoming a benevolent despotism, and perhaps the time will never arrive when such warnings as these will be quite out of date. When it is a question of the oppression of our fellows, we cannot always afford to wait until the offender listens to the voice of persuasion; him, at least, we must bring within “the region of police:” beyond that lies danger.