Now, in connection with many questions of a more or less limited kind, this assimilation of the products of superior ability to rent, and of ability of a lower grade to land which is practically rentless, will serve our purpose well enough. Between the two cases, however, there is a vast and underlying difference; and when we consider our present problem under its widest and most vital aspect, it is the difference, not the likeness, between them, which constitutes our main concern. The nature of this difference has been pointed out already. When we are discussing rent and agriculture, land is a necessary assumption, for unless there were land, there could be no agriculture at all; but there can be, has been, and still is in the world, abundance of labour without directive ability; and while it would be meaningless to ask what would happen to rent if all land disappeared, the question of what would happen to labour if all ability were in abeyance is precisely the question raised by all schemes of economic revolution, and one which has been constantly illustrated by the facts of economic history. Of such facts we may take the following, picturesque example: In the eighteenth century the Jesuit Fathers in Uruguay succeeded in teaching the natives a variety of Western arts, among others that of watch-making, and so long as the Jesuits were on the spot to direct them the natives exhibited much manual skill. But when, owing to political causes, the Jesuits were driven from the country, the natives sank back into their previous industrial helplessness. The temporary efficiency of their labour had been due to the ability that directed it; and as soon as that ability was withdrawn, the labour, left to itself, shrank again to its old relative inefficiency. Now, here we have a case precisely analogous to that which we have to deal with when considering at the present day how much of the products of any civilised nation is produced by the labour of the average units of the population, and how much by the ability of the exceptional men directing them. It is not a question of how much this or that group of labourers, which is directed by a man of the highest grade of ability, produces in excess of the products of some similar group which is directed by another man whose ability is somewhat inferior; it is a question of how much the same nation would produce, if every director of other men's labour were withdrawn, and the present labouring units left to their own devices.