Law has been classified for different purposes and the purpose has determined the classification. The two commonest purposes are those of legislation and of teaching.
The oldest codes that have come down to us, of which one of the most complete is the code of the Babylonian King Hammurabi of about 1800 B.C., make little effort at what seems to us a logical classification.
In this code, as in the Greek codes of the fifth century B.C. as well as in the Twelve Tables, procedure plays a large part. The Corpus juris civilis, so far as the Digest was concerned, seems to have been arranged according to the sources of its material, one part being taken from the praetor’s edict, one from the writings of the Sabinian school, one from Papinian, and one miscellaneous.
Modern codes, beginning with the French Code of 1804, have for the most part followed the divisions introduced by the Institutes of Justinian in A.D. 533. The divisions are two: the law of persons and the law of things.
In the Institutes, inheritance was a part of the law of person, obligations part of the law of things, and penal law part of the law of procedure. Modern codes have separated these classes.
The modern tendency is to classify laws by subject matter, and, where codification is extensively used, there is, as in France, a separate code for each subject; a civil code, a code of criminal procedure, a code of commerce, a maritime code, a military code, an administrative code, and a forest code.
Other jurisdictions, such as California, have an even greater number of codes.
Changes in economic conditions being new matters into prominence and often require new classifications. The importance of labor relations, for example, has made it necessary to segregate “labor law” as a special body of law for purposes of teaching, and while administrative courts have been functioning in France since 1804, the subject of “administrative law” is a relatively new one in common-law countries and is rapidly growing in importance.
Similarly, it has been found advisable to deal with such subjects as “constitutional law,” “tax law,” and a few others as separate categories for purposes of exposition. More limited classifications such as “motor-vehicle” laws illustrate the special effect of new methods of transportation, and “aeronautic law” is one of obviously increasing importance.
In most instances, practical and not logical considerations are paramount in determining classification. Standardization of customs and of social conditions will create a need for common standards in classification which will in them play a large part in standardizing both procedural and substantive law.