Those who maintain that labour, or, as some Socialists assert, the labourer's labour, is the only source of wealth, look merely at the mechanical factor, but omit the force which directs and controls it. The Socialistic argument "We can run the mills without the capitalists, but they cannot run them without us"[157] is misleading. Labour is certainly an indispensable ingredient in production, but it is no more indispensable than is direction, invention, and thrift. Hence it is as absurd to assert "All wealth is due to labour" as to say "All wealth is due to invention," or "All wealth is due to thrift." As the brain is more important than the hand, at least in a highly organised state of production, so invention, organisation, management, and thrift are more important than manual labour, because invention, organisation, management, and thrift alone enable manual labour, working with modern machinery, to be highly productive. In fact, it may be asserted that wealth is created not so much by labour as by the saving of labour. A factory-owner who is dissatisfied with the profits of his factory or with its products does not get better workers, but gets a better manager or better machinery, keeping his workers. This fact proves that labour is the least important factor in modern production. The doctrine "Labour is the only source of wealth" is untenable and absurd. Another fundamental doctrine of Socialism is that of "THE IRON LAW OF WAGES" According to that law, "wages under competition can never be higher than that which will just support the labourer and enable him to renew his kind."[158] In the words of Lassalle, the inventor of the Iron Law of Wages, "the wages of the labourer are limited to the exact amount necessary to keep him alive."[159]