Compared to the work of Diderot, Montesquieu and Rousseau, the philosophical work of Voltaire does not seem to carry much weight. We know Voltaire as a storyteller, poet, playwright, historian, politician... what about Voltaire as a philosopher? The texts brought together in this volume, from his first polemical work – the famous Philosophical Letters – to his latest writings on God, less known, invite us to discover the singularity of Voltairian thought. Written in England, the Philosophical Letters (1734) were “the first bomb launched against the Ancien Régime” (Gustave Lanson): before exploding in the face of royalty by divine right, they condemned their author to exile. Questioning the certainties with which the French of the time were steeped, Voltaire castigates the authorities in place: nourished by the theories of Newton and Locke, he undermines Cartesianism; attacking Pascal, he takes aim at the religious institution. This hostility to the spirit of the system never left him again. Fiercely opposed to the articles of faith, he was also opposed to atheism, as evidenced by the pamphlets written towards the end of his life, from All in God (1769) to It is necessary to take a side (1775) via God (1770) and the Letters of Memmius to Cicero (1771), in which Voltairian deism is clarified in an astonishing synthesis of the ideas of Leibniz, Malebranche and Spinoza.