In other words, when we are seeking to measure the products due respectively to directive ability and to labour, by computing what would happen if either of these agencies were withdrawn, the withdrawal of one of them--that is to say, of ability--can alone be taken as possible by any practical reasoner. We have before us practically two alternatives only. One is a condition of things under which the exceptional ability of the few directs and co-ordinates the labour of the average many. The other is a condition of things under which the labour of the average many has to exert itself with the same severe continuity, but is guided, co-ordinated, and stimulated by none of those special faculties which raise a few men above the general level of efficiency. When these special faculties are applied to the direction of average labour, the output of wealth increases. When their application is interfered with or ceases, the output of wealth declines; and in the only practical sense of the words "cause" or "producer," these faculties of direction, or the exceptional persons who exercise them, are the true causes or producers of the whole of that portion of wealth which comes into being with their activity, and disappears or dwindles with their inaction. The practical validity of this method of computation has been formally recognised, though not completely understood, by some of the later socialists themselves. Mr. Webb, for example, and his associates, have admitted that, of the wealth of the modern world a considerable part consists of "the rent of business ability."[19] This way of expressing the matter is true so far as it goes. It expresses, however, one-half of the truth only. Mr. Webb and his friends mean that, if we take the world as it is, the products due to ability in any given industry consist of the quantity by which the products of one firm, because it is managed by a man of superior talent, exceed the products of another firm which differs from the first only in the fact that it is managed by another man whose talent is not so great. They assume as their starting-point, in every case, the presence of directive ability sufficient to organise the labourers in such a way that the products of the entire group shall provide the labourers with wages which are up to a certain standard, and a minimum of profit or of surplus values besides. This lowest grade of ability is one of the postulates of their argument, just as in calculating agricultural rent the first postulate of our argument is a lowest grade of land.