Comparative law is the study of differences and similarities between the law of different countries. More specifically, it involves study of the different legal "systems" (or "families") in existence in the world, including the common law, the civil law, socialist law, Canon law, Jewish Law, Islamic law, Hindu law, and Chinese law. It includes the description and analysis of foreign legal systems, even where no explicit comparison is undertaken. The importance of comparative law has increased enormously in the present age of internationalism, economic globalization and democratization.
The origins of modern comparative law can be traced back to 18th century Europe, although, prior to that, legal scholars had always practiced comparative methodologies.
Montesquieu is generally regarded as an early founding figure of comparative law. His comparative approach is obvious in the following excerpt from Chapter III of Book I of his masterpiece, De l'esprit des lois (1748; first translated by Thomas Nugent, 1750):
[T]he political and civil laws of each nation ... should be adapted in such a manner to the people for whom they are framed that it should be a great chance if those of one nation suit another.
They should be in relation to the nature and principle of each government: whether they form it, as may be said of politic laws; or whether they support it, as in the case of civil institutions.
They should be in relation to the climate of each country, to the quality of its soil, to its situation and extent, to the principal occupation of the natives, whether husbandmen, huntsmen, or shepherds: they should have relation to the degree of liberty which the constitution will bear; to the religion of the inhabitants, to their inclinations, riches, numbers, commerce, manners, and customs.
Also, in Chapter XI (entitled 'How to compare two different Systems of Laws') of Book XXIX, discussing the French and English systems for punishment of false witnesses, he advises that "to determine which of those systems is most agreeable to reason, we must take them each as a whole and compare them in their entirety." Yet another place where Montesquieu's comparative approach is evident is the following, from Chapter XIII of Book XXIX: