So much is evident with respect to labour rent, the simplest and most primitive form of rent: Rent is here the primeval form of surplus-labour and coincides with it. But this identity of surplus-value with unpaid labour of others need not be analysed here because it still exists in its visible, palpable form, since the labour of the direct producer for himself is still separated in space and time from his labour for the landlord and the latter appears directly in the brutal form of enforced labour for a third person. In the same way the "attribute" possessed by the soil to produce rent is here reduced to a tangibly open secret, for the disposition to furnish rent here also includes human labour-power bound to the soil, and the property relation which compels the owner of labour-power to drive it on and activate it beyond such measure as is required to satisfy his own indispensable needs. Rent consists directly in the appropriation of this surplus expenditure of labour-power by the landlord; for the direct producer pays him no additional rent. Here, where surplus-value and rent are not only identical but where surplus-value has the tangible form of surplus-labour, the natural conditions or limits of rent, being those of surplus-value in general, are plainly clear. The direct producer must 1) possess enough labour-power, and 2) the natural conditions of his labour, above all the soil cultivated by him, must be productive enough, in a word, the natural productivity of his labour must be big enough to give him the possibility of retaining some surplus-labour over and above that required for the satisfaction of his own indispensable needs. It is not this possibility which creates the rent, but rather compulsion which turns this possibility into reality. But the possibility itself is conditioned by subjective and objective natural circumstances. And here too lies nothing at all mysterious. Should labour-power be minute, and the natural conditions of labour scanty, then the surplus-labour is small, but in such a case so are the wants of the producers on the one hand and the relative number of exploiters of surplus-labour on the other, and finally so is the surplus-product, whereby this barely productive surplus-labour is realised for those few exploiting landowners.