No one will deny that when a play like “Man and Superman” first acquires a vogue which renders its performance profitable, the royalties paid to the author are values which he has himself created, not indeed by his faculties used directly, but by his faculties embodied in a work which he has accomplished once for all in the past, and which has thenceforward become a secondary and indefinitely enduring self; and if this is true of the royalties resulting from its first profitable performance, it would be equally true of those resulting from the last, even though this should take place on the eve of the Day of Judgment.  With productive machinery the case is just the same.  If Mr. Shaw, instead of writing “Man and Superman,” had been the sole inventor of the steam-engine, and the only man capable of inventing it, every one will admit that he would, by this one inventive effort, have personally co-operated for a time with all users of steam-power, and been part-producer of the increment in which its use resulted.  And if this would have been true of his invention when it was only two years old, it would be equally true now.  He would still be co-operating with the users of every steam-engine in the world to-day, and adding to their products something which they could not have produced alone.

Here, then, we see that in one respect at all events the two kinds of capital, which George attempts to contrast, yield interest for a precisely similar reason.  Both consist of a productive power or agency which is external to the borrower himself; and it makes no difference to him whether the auxiliary power borrowed inheres in living tissue, or in a mechanism of brass or iron.

But the resemblance between these two forms of capital, and the identity of the reasons why both of them bear interest, do not end here.  I quoted in a former chapter an observation of Mr. Sidney Webb’s, which he himself applies in a very foolish way, but which is obviously true in itself, and in the present connection is pertinent.  Some men he admits are incomparably more productive than others, because they happen to be born with a special kind of ability.  But what is this ability itself?  It is simply the result, he says, of a process which lies behind them—­namely, the natural process of animal and human evolution; and its special products are like those of exceptionally fertile land.  That is to say, the ability which produces modern machines is in reality just as much a force of nature as that which makes live-stock fertile, and brings raw wine to maturity.  But the same line of argument will carry us much farther than this.  As Dr. Beattie Crozier has shown in his work, The Wheel of Wealth, the part which nature plays in productive machinery is not confined to the brains of the gifted inventors and their colleagues.  It is incorporated in, and identified with, the actual machines themselves.  The lever, the cam, the eccentric, the crank, the piston, the turbine, the boiler with the vapour imprisoned