The foregoing history, apart from the purposes for which it has been given, well illustrates the paradox of form and substance in the development of law. In form its growth is logical. The official theory is that each new decision follows syllogistically from existing precedents. But just as the clavicle in the cat only tells of the existence of some earlier creature to which a collar-bone was useful, precedents survive in the law long after the use they once served is at an end and the reason for them has been forgotten. The result of following them must often be failure and confusion from the merely logical point of view. On the other hand, in substance the growth of the law is legislative. And this in a deeper sense than that what the courts declare to have always been the law is in fact new. It is legislative in its grounds. The very considerations which judges most rarely mention, and always with an apology, are the secret root from which the law draws all the juices of life. I mean, of course, considerations of what is expedient for the community concerned. Every important principle which is developed by litigation is in fact and at bottom the result of more or less definitely understood views of public policy; most generally, to be sure, [36] under our practice and traditions, the unconscious result of instinctive preferences and inarticulate convictions, but none the less traceable to views of public policy in the last analysis. And as the law is administered by able and experienced men, who know too much to sacrifice good sense to a syllogism, it will be found that, when ancient rules maintain themselves in the way that has been and will be shown in this book, new reasons more fitted to the time have been found for them, and that they gradually receive a new content, and at last a new form, from the grounds to which they have been transplanted. But hitherto this process has been largely unconscious. It is important, on that account, to bring to mind what the actual course of events has been. If it were only to insist on a more conscious recognition of the legislative function of the courts, as just explained, it would be useful, as we shall see more clearly further on. /1/ What has been said will explain the failure of all theories which consider the law only from its formal side; whether they attempt to deduce the corpus from a priori postulates, or fall into the humbler error of supposing the science of the law to reside in the elegantia juris, or logical cohesion of part with part. The truth is, that the law always approaching, and never reaching, consistency. It is forever adopting new principles from life at one end, and it always retains old ones from history at the other, which have not yet been absorbed or sloughed off. It will become entirely consistent only when it ceases to grow.