[Footnote 29: Joyce, _Social History of Ancient Ireland_, i. 181.] The transformation of customs into laws was not a mere ceremony. Law, like custom, is a rule of conduct, but, while custom is established by usage and obtains, in a more or less indefinite way, its binding force from public opinion, a law originates in a definite legislative act, being set, as Austin says, by a sovereign person, or a sovereign body of persons, to a person or persons in a state of subjection to its author.[30] By becoming laws, then, the customs were expressly formulated, and were enforced by a more definite sanction. It seems that the process in question arose both from considerations of social utility and from a sense of justice. Cicero observes that it was for the sake of equity that "laws were invented, which perpetually spoke to all men with one and the same voice."[31] From these points of view it was neither necessary nor desirable that more than a limited set of customs should pass into laws. There are customs which are too indefinite to assume the stereotyped shape of law.[32] There are others, the breach {166} of which excites too little public indignation, or which are of too little importance for the public welfare, to be proper objects of legislation. And there are others which may be said to exist unconsciously, that is, which are universally observed as a matter of course, and which, never being transgressed, are never thought of. [Footnote 30: Austin, _Lectures on Jurisprudence_, i. 87, 181, &c.] [Footnote 31: Cicero, _De officiis_, ii. 12.] [Footnote 32: _Cf._ Aristotle, _Ethica Nicomachea_, v. 10. 6.] Laws which are based on customs naturally express moral ideas prevalent at the time when they are established. On the other hand, though still in existence, they are not necessarily faithful representatives of the ideas of a later age. Law may be even more conservative than custom. Though the latter exercises a very preservative influence on public opinion, it _eo ipso_ changes when public opinion changes. Even among savages, in spite of their extreme regard for the customs of their ancestors, it is quite possible for changes to be introduced; the traditions of the Central Australian Arunta, for instance, indicate their own recognition of the fact that customs have varied from time to time.[33] But the legal form gives to an ancient custom such a fixity as to enable it to survive, as a law, the change of public opinion and the introduction of a new custom. In all progressive societies, as Sir Henry Maine observes, social necessities and social opinion are always more or less in advance of law. "We may come indefinitely near to the closing of the gap between them, but it has a perpetual tendency to re-open."[34] [Footnote 33: Spencer and Gillen, _Native Tribes of Central Australia_, p. 12 _sqq._] [Footnote 34: Maine, _Ancient Law_, p. 24.]