Having stated his general doctrine, Montesquieu proceeds to apply it. As laws should be adapted to the nature of the government of each country, it is essential to study that nature, and to consider what is the _principle_, or motive force of each form of government. "There is this difference," he says, "between the nature of the government and its principle: that its nature is what makes it such as it is, and its principle what makes it act. One is its especial structure, and the other the human passions which cause it to operate."[Footnote: Montesq., iii, 120 (liv. iii. c. 1).] Four kinds of government are recognized by Montesquieu: democratic, aristocratic, monarchical, and despotic. The principle of democracy he holds to be _virtue_, without which popular government cannot continue to exist.[Footnote: Montesq., iii. 122 (liv. iii. c. 3).] An aristocratic state needs less virtue, because the people is kept in check by the nobles. But the nobility can with difficulty repress the members of their own order, and do justice for their crimes. In default of great virtue, however, an aristocratic state can exist if the ruling class will practice _moderation_.[Footnote: Ibid., iii. 126 (liv. c. 4).] In monarchies great things can be done with little virtue, for in them there is another moving principle, which is honor.[Footnote: Ibid., iii. 128 (liv. iii. c. 5, 6, and 7).] This sort of government is founded on the prejudice of each person and each sort of men; it rests on ranks, preferences, and distinctions, so that emulation often supplies the place of virtue. In a monarchy there will be many tolerable citizens, but seldom a very good man, who loves the state better than himself. The motive principle of a despotism is _fear_[Footnote: Ibid., iii. 135 (liv. iii. c. 9).]; for in despotic states virtue is unnecessary, and honor would be dangerous. These qualities of virtue, honor, and fear, may not exist in every republic, monarchy, and despotism; but they should do so, if the government is to be perfect of its kind.[Footnote: Ibid., iii. 140 (liv. iii. c. 11).] It is worth while to remember, when considering the "Spirit of the Laws," that Montesquieu oftenest had in his mind, when speaking of democratic republics, those of Greece; when speaking of aristocratic republics, early Rome and Venice; of monarchies, France and England; of despotisms, the East.[Footnote: But he sometimes refers to England as a country where a republic is hidden under the forms of a monarchy. Montesq, iii. 216 (liv. V. c. 19).]