The concept of history of legislation relates to the narration of the rules and laws that constitute civil governments and of those acts expressed in the form of common precepts intended to regulate reciprocal relations in human society.
German philosopher Gottfried Leibniz (1646-1716) was the first to make the distinction in the history of law in terms of form between internal and external, the former dealing with its substance and the latter being the substantiation and requisite of the former, that is, it supports the treatment of the subject. In other words, the external history provides the reasons and the evidence that justify the internal.