Now, of certain forms of effort this may be true enough.  A bricklayer, for example, as soon as he ceases to lay bricks, ceases to produce anything.  His wall-building closes its effects with the walls which he himself has built.  It does nothing to facilitate the building of other walls in the future.  Similarly such ability as consists in a gift for personal management often ends its effects, and leaves no trace behind it, as soon as the manager possessing these gifts retires.

But with many forms of ability the case is precisely opposite.  The products of their exercise do not even begin to appear till after—­often till long after—­the exercise of the ability itself has altogether come to an end.  Let us, for example, take the case of a play; and since socialists are still included among the objectors whom we have in view, let us take one of the popular plays written by Mr. Bernard Shaw.  Such a play, as Mr. Shaw has publicly boasted—­for otherwise I should not mention, and should know nothing of his private affairs—­brings to its author wealth in the form of amazing royalties; but until it is acted it brings him no royalties at all, and the actors begin with it only when his own efforts are ended.  Moreover, not only do these royalties only begin then, but having once begun, they have no tendency to exhaust themselves.  On the contrary the chances are that they will go on increasing till the time arrives, if it ever does, when Mr. Shaw is no longer appreciated.  Mr. Shaw, in fact, if he had written one of his most successful plays at twenty, might, so far as that play is concerned, be idle for ever afterwards, even if he lived to the age of Methuselah, and still be enjoying in royalties the product of his own exertions, though he had not exerted himself productively for some seven or eight hundred years.

There is no question here of whether, under these conditions, a person like Mr. Shaw might not feel himself constrained on some ground or other to surrender his copyright at some period prior to his own demise.  The one point here insisted on is that he could not renounce it on the ground that the wealth protected by it was no longer produced by himself.  If he is entitled to the royalties resulting from the performance of his play at any time, on the ground that every man has a right to the products of his own exertions, his right to the royalties resulting from its ten-thousandth performance is, on this ground, as good as his right to the royalties resulting from the first.  The royalties on a play, in short, show how certain forms of effort, though not all, continue to yield a product for an indefinite period, though the original effort itself may be never again repeated; and herein these royalties are typical of modern interest generally.  They do not, however, constitute in themselves more than a small part of it.  We will therefore turn to interest of other kinds, the details of whose genesis are indeed widely different, but which consist similarly of a constant repetition of values, without any corresponding repetition of the effort in which the series originated.