These two questions, though not mutually exclusive, differ as much as the question of why one of two balloons rises above the earth to a height of three miles and a furlong, while a second balloon reaches the height of three miles only, differs from the question of why either of them rises in the air at all. Mr. Webb and his friends, with their theory of the rent of ability, confine themselves to the first of these--namely, the question of why one balloon rises a furlong higher than the other. The real question which we have to deal with here is why both balloons lift their aeronauts at least three miles into the clouds, while other men who have no balloon to lift them can get no higher than the top of the church steeple. Or to come back to literal fact, our problem must be expressed thus: Let us take the present population of Great Britain or America, and, having noted the wealth at present annually produced by it, ask ourselves what would happen if some duly qualified angel were to pick out and kill, or otherwise make away with, every man, who, in virtue of his assimilated scientific knowledge, his inventive gifts, his constructive and practical imagination, his energy, his initiative, and his natural powers of leadership, was better able to direct others than the other nine were to direct themselves? We cannot make this experiment in precisely the way described; but history will provide us with equivalents which are sufficiently accurate for our purpose. There are, for example, in the case of Great Britain, data which have enabled statisticians with a considerable degree of unanimity to estimate the values produced per head of the industrial population at various periods from the reign of Charles II. till to-day, and to reduce these values to comparable terms of money. Now, we need not insist too much on the accuracy of the figures in question; but one broad fact is unmistakably shown by them--that the product per head towards the close of the nineteenth century was, to say the least of it, from four to five times as great as it was towards the close of the sixteenth. To what, then, was this increase in industrial productivity due? It was not due to any change in the spontaneous workings of nature. It can only have been due to some change in the character of human effort--either in that of the effort of each separate manual labourer, or else in that of the men by whom the labour of others is directed. The average labourer, however, at the close of the nineteenth century did not differ, as an isolated labouring unit, from the average labourer as he was at the time of the fire of London. The increase in industrial productivity must therefore be necessarily due to a change in the ability of those by whom the labourers are organised and directed. And here _a priori_ reasoning is confirmed by actual facts, for the change which has taken place in the class which directs the labour of others