Abstract: Nature is one of the central ideas of modern Western thought. While keeping with the tradition of natural law of the seventeenth century, Montesquieu incorporated history, culture and geographical environment into his reflection on nature, and explored its physical, social and moral aspects. In his view, physical nature concerns the function of the universe and the physiological existence of animals and human beings. Social nature refers to the individual and collective mentality forged by human creations such as politics, laws, societies, religions and so on. In Persian Letters and Considerations on the Causes of the Grandeur and Declension of the Roman Empire, Montesquieu described how the spiritual habits of the individual and the nation were shaped by political principles and social customs. Moral nature consisted of universal and rational moral requirements that included natural law, equitable relations and moral norms. Moral nature defined moral norms for human actions, however, in life, physical nature and social nature often distorted or even destroyed moral nature. Montesquieu pointed out that slavery deviated from moral nature in all aspects, but agreed that the extremely hot climate might offer rationality for forced labor. For him, this was not an acknowledgement of the legitimacy of slavery, instead, an example that illustrated the violation of moral nature by physical nature. Montesquieu put the polities in history into three categories of republic, monarchy and despotism, each representing principles of virtue, honor and fear respectively. In a democratic republic, virtue was embodied in the love for motherland and equality. It requires citizens to suppress or even sacrifice their natural feelings and interests for the benefit of the motherland. In an aristocratic republic, order was obtained by disciplines of the nobility, which required very violent means to maintain. Honor as the principle of monarchy was nothing but a product of vanity and pride, often mixed with moral defects and vices. Fear in despotism was a degrading force trampling on human nature. Therefore, the principles of these three polities more or less deviated from moral nature. However, Montesquieu did not deny the rationality of the existence of these three types of regimes. With detailed analyses of various political systems and laws, particularly the history of politics and commerce, he argued that the modern commercial republic represented by England was most conducive to the realization of moral nature. Commerce promoted peace and gentleness of the people, and to a large extent, satisfied people's natural interests and emotions. Constitutionalism that guaranteed human rights provided liberty and security for individuals. Although commerce and constitutionalism were not without defects, Montesquieu considered the modern liberal commercial republic based on both as a good political system favorable to moral nature. Nevertheless, he did not suggest that every nation should proceed to imitate England. Instead, Montesquieu stressed that lawmakers of each nation should choose its own form of government according to its social and moral nature, and should consider the relationship and tension among the three dimensions of nature in order to carry out moderate and prudent enlightenment and reform.

Key words: Montesquieu, nature, society, commerce, enlightenment