The Spirit of Law

Constitutional theory

In his classification of political systems, Montesquieu defines three main kinds: republican, monarchical, and despotic. As he defines them, Republican political systems vary depending on how broadly they extend citizenship rights—those that extend citizenship relatively broadly are termed democratic republics, while those that restrict citizenship more narrowly are termed aristocratic republics. The distinction between monarchy and despotism hinges on whether or not a fixed set of laws exists that can restrain the authority of the ruler: if so, the regime counts as a monarchy; if not, it counts as despotism.

Principles that motivate citizen behavior according to Montesquieu

Driving each classification of political system, according to Montesquieu, must be what he calls a "principle". This principle acts as a spring or motor to motivate behavior on the part of the citizens in ways that will tend to support that regime and make it function smoothly.

• For democratic republics (and to a somewhat lesser extent for aristocratic republics), this spring is the love of virtue—the willingness to put the interests of the community ahead of private interests.
• For monarchies, the spring is the love of honor—the desire to attain greater rank and privilege.
• Finally, for despotisms, the spring is the fear of the ruler—the fear of consequences to authority.

A political system cannot last long if its appropriate principle is lacking. Montesquieu claims, for example, that the English failed to establish a republic after the Civil War (1642–1651) because the society lacked the requisite love of virtue.

Liberty and the separation of powers

A second major theme in The Spirit of Law concerns political liberty and the best means of preserving it. "Political liberty" is Montesquieu's concept of what we might call today personal security, especially in so far as this is provided for through a system of dependable and moderate laws. He distinguishes this view of liberty from two other views of political liberty. The first is the view that liberty consists in collective self-government—i.e. that liberty and democracy are the same. The second is the view that liberty consists in being able to do whatever one wants without constraint. Not only are these latter two not genuine political liberty, he maintains, but they can both be hostile to it.

Political liberty is not possible in a despotic political system, but it is possible, though not guaranteed, in republics and monarchies. Generally speaking, establishing political liberty on a sound footing requires two things:

• The separation of the powers of government.

Building on and revising a discussion in John Locke's Second Treatise of Government, Montesquieu argues that the executive, legislative, and judicial functions of government should be assigned to different bodies, so that attempts by one branch of government to infringe on political liberty might be restrained by the other branches. (Habeas corpus is an example of a check that the judicial branch has on the executive branch of government.) In a lengthy discussion of the English political system, he tries to show how this might be achieved and liberty secured, even in a monarchy. He also notes that liberty cannot be secure where there is no separation of powers, even in a republic.

• The appropriate framing of civil and criminal laws so as to ensure personal security.

Montesquieu intends what modern legal scholars might call the rights to "robust procedural due process", including the right to a fair trial, the presumption of innocence and the proportionality in the severity of punishment. Pursuant to this requirement to frame civil and criminal laws appropriately to ensure political liberty (i.e., personal security), Montesquieu also argues against slavery and for the freedom of thought, speech and assembly.

This book mainly concerns explicit laws, but also pays considerable attention to cultural norms that may support the same goals. "Montesquieu believed the hard architecture of political institutions might be enough to constrain overreaching power — that constitutional design was not unlike an engineering problem," as Levitsky and Ziblatt put it.

Political sociology

The third major contribution of The Spirit of Law was to the field of political sociology, which Montesquieu is often credited with more or less inventing. The bulk of the treatise, in fact, concerns how geography and climate interact with particular cultures to produce the spirit of a people. This spirit, in turn, inclines that people toward certain sorts of political and social institutions, and away from others. Later writers often caricatured Montesquieu's theory by suggesting that he claimed to explain legal variation simply by the distance of a community from the equator.

While the analysis in The Spirit of Law is much more subtle than these later writers perceive, many of his specific claims lack rigour to modern readers. Nevertheless, his approach to politics from a naturalistic or scientific point of view proved very influential, directly or indirectly inspiring modern fields of political science, sociology, and anthropology.

Further reading in English

• Sheila Mason, Montesquieu’s Idea of Justice, The Hague: Martinus Nijhoff, 1975.
• Mark Hulliung, Montesquieu and the Old Regime, Berkeley: University of California Press, 1976.
• Stephen J. Rosow, "Commerce, Power and Justice: Montesquieu on international politics," Review of Politics 46, no. 3 (July 1984): 346–366.
• Anne M. Cohler, Montesquieu’s Comparative Politics and the Spirit of American Constitutionalism, Lawrence KS: University Press of Kansas, 1988.
• Thomas L. Pangle, Montesquieu’s Philosophy of Liberalism: a commentary on "The Spirit of the Laws", Chicago: University of Chicago Press, 1989.
• David W. Carrithers, "Montesquieu’s philosophy of punishment," History of Political Thought 19 (1998), p. 213-240.
• David W. Carrithers, Michael A. Mosher, and Paul A. Rahe, eds., Montesquieu’s Science of Politics: essays on "The Spirit of Laws", Lanham, Maryland: Rowman & Littlefield, 2001.
• Robert Howse, "Montesquieu on Commerce, War, and Peace," Brookings Journal of International Law 31, no. 3 (2006): 693–708. http://www.law.nyu.edu/sites/default/files/ECM_PRO_060042.pdf
• Paul A. Rahe, Montesquieu and the Logic of Liberty, New Haven: Yale University Press, 2009.
• Andrea Radasanu, "Montesquieu on Moderation, Monarchy and Reform," History of Political Thought 31, no. 2 (2010), p. 283–307.
• Rolando Minuti, Studies on Montesquieu: mapping political diversity, Cham (Switzerland): Springer, 2018. (Translation by Julia Weiss of Una geografia politica della diversità: studi su Montesquieu, Naples, Liguori, 2015.)
• Andrew Scott Bibby, Montesquieu’s Political Economy, New York: Palgrave Macmillan, 2016.
• Joshua Bandoch, The Politics of Place: Montesquieu, particularism, and the pursuit of liberty, Rochester: University of Rochester Press, 2017.
• Vickie B. Sullivan, Montesquieu and the Despotic Ideas of Europe: an interpretation of "The Spirit of the laws", University of Chicago Press, 2017.
• Keegan Callanan, Montesquieu’s Liberalism and the Problem of Universal Politics, New York: Cambridge University Press, 2018.
• Sharon R. Krause, The Rule of Law in Montesquieu, Cambridge University Press, 2021.
• Vickie V. Sullivan, "Montesquieu on Slavery," in K. Callanan, The Cambridge Companion to Montesquieu, New York, 2023, p. 182-197.