This practical conclusion [that interest on capital oppresses the working classes] has been supported by other arguments which will claim our attention; but at present we are only concerned with the doctrine that has been used by William Thompson, Rodbertus, Karl Marx, and others in support of it. They argued that labour always produces a “Surplus” above its wages and the wear-and-tear of capital used in aiding it: and that the wrong done to labour lies in the exploitation of this surplus by others. But this assumption that the whole of this Surplus is the produce of labour, already takes for granted what they ultimately profess to prove by it; they make no attempt to prove it; and it is not true. It is not true that the spinning of yarn in a factory, after allowance has been made for the wear-and-tear of the machinery, is the product of the labour of the operatives. It is the product of their labour, together with that of the employer and subordinate managers, and of the capital employed; and that capital itself is the product of labour and waiting: and therefore the spinning is the product of labour of many kinds, and of waiting. If we admit that it is the product of labour alone, and not of labour and waiting, we can no doubt be compelled by inexorable logic to admit that there is no justification for Interest, the reward of waiting; for the conclusion is implied in the premiss. Rodbertus and Marx do indeed boldly claim the authority of Ricardo for their premiss; but it is really as opposed to his explicit statement and the general tenor of his theory of value, as it is to common sense.
To put the same thing in other words; if it be true that the postponement of gratifications involves in general a sacrifice on the part of him who postpones, just as additional effort does on the part of him who labours; and if it be true that this postponement enables man to use methods of production of which the first cost is great; but by which the aggregate of enjoyment is increased, as certainly as it would be by an increase of labour; then it cannot be true that the value of a thing depends simply on the amount of labour spent on it. Every attempt to establish this premiss has necessarily assumed implicitly that the service performed by capital is a “free” good, rendered without sacrifice, and therefore needing no interest as a reward to induce its continuance; and this is the very conclusion which the premiss is wanted to prove. The strength of Rodbertus’ and Marx’s sympathies with suffering must always claim our respect: but what they regarded as the scientific foundation of their practical proposals appears to be little more than a series of arguments in a circle to the effect that there is no economic justification for interest, while that result has been all along latent in their premisses; though, in the case of Marx, it was shrouded by mysterious Hegelian phrases, with which he “coquetted,” as he tells us in his Preface.
— Marshall - Principles of Economics (8th Ed.), book VI, ch. 6, §3