The whole of his mind--almost the whole of his existence--is embodied in the _Esprit des Lois_ (1748). It lacks the unity of a ruling idea; it is deficient in construction, in continuity, in cohesion; much that it contains has grown obsolete or is obsolescent; yet in the literature of eighteenth-century thought it takes, perhaps, the highest place; and it must always be precious as the self-revealment of a great intellect--swift yet patient, ardent yet temperate, liberal yet the reverse of revolutionary--an intellect that before all else loved the light. It lacks unity, because its author's mind was many-sided, and he would not suppress a portion of himself to secure a factitious unity. Montesquieu was a student of science, who believed in the potency of the laws of nature, and he saw that human society is the product of, or at least is largely modified by, natural law; he was also a believer in the power of human reason and human will, an admirer of Roman virtue, a citizen, a patriot, and a reformer. He would write the natural history of human laws, exhibit the invariable principles from which they proceed, and reduce the study of governments to a science; but at the same time he would exhibit how society acts upon itself; he would warn and he would exhort; he would help, if possible, to create intelligent and patriotic citizens. To these intentions we may add another--that of a criticism, touched with satire, of the contemporary political and social arrangements of France. And yet again, Montesquieu was a legist, with some of the curiosity of an antiquary, not without a pride in his rank, interested in its origins, and desirous to trace the history of feudal laws and privileges. The _Esprit des Lois_ is not a doctrinaire exposition of a theory, but the record of a varied life of thought, in which there are certain dominant tendencies, but no single absolute idea. The forms of government, according to Montesquieu, are three--republic (including both the oligarchical republic and the democratic), monarchy, despotism. Each of these structural arrangements requires a principle, a moral spring, to give it force and action: the popular republic lives by virtue of patriotism, public spirit, the love of equality; the aristocratic republic lives by the spirit of moderation among the members of the ruling class; monarchy lives by the stimulus of honour, the desire of superiority and distinction; despotism draws its vital force from fear; but each of these principles may perish through its corruption or excess. The laws of each country, its criminal and civil codes, its system of education, its sumptuary regulations, its treatment of the relation of the sexes, are intimately connected with the form of government, or rather with the principle which animates that form.