Among the pioneers of the new doctrines two men stand out conspicuously in each half of the century,--Montesquieu and Voltaire in the first half, Diderot and Rousseau in the second. Montesquieu, the earliest of the philosophers, was a polished and eminent lawyer, well versed in history, serious, acute, a profound student of human institutions, and the master of a terse and pointed style. His writings, generally speaking, were no mere flights of pert fancy, but the result of systematised and careful thought, weighty, luminous, moderate in tone, and scientifically sane. It was Montesquieu, who, in his _Lettres Persanes_, initiated the philosophic movement, and unmasked the batteries of criticism and satire, which for two generations were to play so effectively upon the foundations of the old monarchy in France. It was Montesquieu, who, twenty seven years later, when he produced the great work of his life, the _Esprit des Lois_, analysed with clear and wide sagacity the laws which regulate human governments and customs, and thus destroyed the mysterious prestige which had never till then been stripped from the ancient institutions of France. It was Montesquieu, who first exposed those institutions to a ruthless analysis which they could not stand. But the slow and careful method, which was Montesquieu's distinction, was less popular with his successors. It involved too much trouble. It ran the risk, except in a master's hands, of being dull. The classical spirit, the French temperament, the love of amusement combined to guide criticism into an easier groove, and the philosophic movement, without altogether deserting the studious atmosphere of facts, adopted a more becoming garment in the exquisite raillery of Voltaire. Voltaire's life extended long past the middle of the century, and its closing years were the years of its greatest triumphs. But he yet belongs to the generation of Montesquieu rather than to that of Rousseau. Under him, the tone of the new movement altered. It became lighter, and bolder too. Its reserve vanished. Its intrepidity increased. It entered every field. It illumined every subject. In verse, in prose, in history, in drama, in romance, Voltaire assailed traditions, beliefs, abuses, exposing mercilessly their shortcomings and shifts, laughing aloud over their absurdities, denying the pretensions which they boasted, denouncing the iniquities to which they led. Voltaire's rare and versatile wit, his light touch, his unabashed scepticism, his brilliant common-sense, appealed irresistibly to the minds of his countrymen. He made the philosophic movement popular. He identified it with many errors, and with the gravest faults of taste. But with it all he taught men to despise many follies and to impeach many wrongs.