Note al — Chapter V

The term "relativity" is employed here on account of its breadth and comprehensiveness, and because it does not imply the adoption of some special hypothesis as to the essence of things or formative principles themselves;—such theorizing being no necessary condition of the present line of thought.

Let it be observed, however, that any law of the natural world by virtue of which, the apprehended relativity becomes operative, must be conceived as in its own nature genetic or causative, in order to explain Production. What is here meant may easily be understood by a few common-sense reflections.

The word "Law" is one of the most ambiguous expressions possible. Perhaps its most familiar use is in statistical science, where it usually means the result gained from averages. For example, birth-rates, death-rates, and rates of exchange are spoken of as laws of increase, of mortality, and of the money market. Sometimes nothing but the generalized fact is signified; sometimes it is intended to imply that these formulæ govern, or ought to govern social questions, or problems of political economy.

In like manner, when a law is the verbal embodiment of any principle, it may be considered as a perfectly abstract proposition; or else as a governing rule or maxim, under which definite and actual cases can be brought. The principles of arithmetic or geometry are laws to which every practical question involving number or measurement must be submitted. The laws of thought govern our reasonings, or at least they ought to do so.

Another way of looking at Law is to consider it in its commonest origin—i.e., as the expression of a law-maker's will. But when a writer on Natural Theology speaks of the laws of the physical world, and then adds that "law implies a lawgiver," he either supposes himself to have demonstrated the applicability of this maxim in relation to his own science;—or if not he is simply assuming the whole question at issue. [Compare Additional Note B, to Chapter II. p. 98, seq.]

The remaining most usual employment of the word, is to designate a Force, some actual moving power tending to realize itself in some way, working out a function either for good or evil, developing the secret of its own existence by the effects which it produces.

Take an example from real life. A medical man coming to a certain rural district, observed its high death-rate, traced it to the very great prevalence of small-pox in the place, and formulated a law embodying the results of several years averages which appeared sufficiently surprising. A further acquaintance with the habits of the neighbourhood disclosed the fact that inoculation was continually practised, and as continually kept secret on account of the penalties attached to it. The inquirer took advantage of the opportunity afforded by a custom he could not control to investigate its consequences. A few years later, he arrived at exact conclusions determining the law of activity exerted by the virus, under certain conditions. In other words, he found the genetic law of its operation.

Now, if the death-rate,—a piece of statistical law,—be contrasted with this last named law of virus-growth, the difference between these two formulæ is at once obvious. Without any scientific discussion or refining, we grasp a broad common-sense distinction, which is all that seems needed here. For our purpose, it would be useless to inquire whether the law of virus-growth may be resolved into laws higher and far more recondite still. An inventor seizing the useful law he wants, will not stop to ask any such questions; he will apply his power and realize the function he has in view at the moment.

Another common-sense instance is to think of the properties of any familiar substance; the acridity of an alkali, for instance; its power of effervescing with acids, and neutralizing them; its behaviour as a reagent in a variety of ways, long to enumerate, but practically useful. When we have described all these properties, have we defined the whole substance? In other words, is the alkali anything more than a bundle of properties momentarily known to us? Undoubtedly there is one point more to be noticed; its principle of permanence, until brought under new conditions which dissolve its unity, and destroy the inter-coherence of its properties. Now whatever maintains this unity is the law of its substance. There are laws of nature under which both it and countless other substances are formed, continue, and are dissolved, making way for unending series of fresh combinations. And this mode of apprehending the unities we call substances, raises the self-same idea of genetic law which has been under consideration. If we are asked whether we can explain such laws further, we usually reply by saying "these are the forces of the natural world." Their correlations and modifications rule the kingdom of nature, and the great globe itself;—nay, they wield the empire of the Universe!

Such laws, such forces, have engrossed the attention of physical philosophers from the rude beginnings of inquiry. They have led to speculations of all kinds;—the best known of which is the distinction between Form and Matter in existing objects;—a distinction in common use amongst persons who but dimly guess at the past issues which it raises. Nothing, however, can be said on such a topic here, except by way of reference to the philosophic system of Francis Bacon. [Compare p. 92 ante, and the Synopsis prefixed to this chapter.]