However, let us see what Sismondi has to say about the origin of these three kinds of income which betray a rift in the foundations of society. He is right to take a certain development of labour productivity as his point of departure. 'By reason of the advances both in industry and science, by which man has subjugated the forces of nature, every worker can produce more, far more, in a day than he needs to consume.'[160] Sismondi thus rightly stresses the fact that the productivity of labour is an indispensable condition for the historical foundation of exploitation. Yet he goes on to explain the actual origin of exploitation in a way typical of bourgeois economics: 'But even though his labour produces wealth, this wealth, if he is called upon to enjoy it, will make him less and less fit for work. Besides, wealth hardly ever remains in the possession of the man who must live by the work of his hands.'[160] Thus he makes exploitation and class antagonism the necessary spur to production, quite in accord with the followers of Ricardo and Malthus. But now he comes to the real cause of exploitation, the divorce of labour power from the means of production. 'The worker cannot, as a rule, keep the land as his own; land, however, has a productive capacity which human labour but directs to the uses of man. The master of the land on which labour is performed, reserves a share in the fruits of labour to which his land has contributed, as his remuneration for the benefits afforded by this productive capacity.'[161] This is called rent. And further: 'In our state of civilisation, the worker can no longer call his own an adequate fund of objects for his consumption, enough to live while he performs the labours he has undertaken--until he has found a buyer. He no longer owns the raw materials, often coming from far away, on which he must exercise his industry. Even less does he possess that complicated and costly machinery which facilitates his work and makes it infinitely more productive. The rich man who possesses his consumption goods, his raw materials and his machines, need not work himself, for by supplying the worker with all these, he becomes in a sense the master of his work. As reward for the advantages he has put at the worker's disposal, he takes outright the greater part of the fruits of his labour.'[162] This is called capital profits. What remains of wealth, after the cream has been taken off twice, by landlord and capitalist, is the wage of labour, the income of the worker. And Sismondi adds: 'He can consume it without reproduction.'[163]