The subjective essence of private property, private property as activity for itself, as subject, as person, is labor. It, therefore, goes without saying that only that political economy which recognized labor as its principle (Adam Smith), and which therefore no longer regarded private property as nothing more than a condition external to man, can be regarded as both a product of the real energy and movement of private property (it is the independent movement of private property become conscious of itself, it is modern industry as self), a product of modern industry, and a factor which has accelerated and glorified the energy and development of this industry and transformed it into a power belonging to consciousness.
Therefore, the supporters of the monetary and mercantile system, who look upon private property as a purely objective being for man, appear as fetish-worshippers, as Catholics, to this enlightened political economy, which has revealed – within the system of private property – the subjective essence of wealth. Engels was, therefore, right to call Adam Smith the Luther of political economy [in Engels 1843 Outlines of a Critique of Political Economy]. Just as Luther recognized religion and faith as the essence of the external world and, in consequence, confronted Catholic paganism; just as he transcended religion external religiosity by making religiosity the inner essence of man; just as he negated the idea of priests as something separate and apart from the layman by transferring the priest into the heart of the layman; so wealth as something outside man, and independent of him – and, therefore, only to be acquired acquired and maintained externally – is abolished [aufgehoben]. i.e., its external and mindless objectivity is abolished inasmuch as private property is embodied in man himself and man himself is recognized as its essence – but this brings man himself into the province of religion.
So, although political economy, whose principle is labor, appears to recognize man, it is, in fact, nothing more than the denial of man carried through to its logical conclusion: for man himself no longer stands in a relation of external tension to the external essence of private property – he himself has become the tense essence of private property. What was formerly being-external-to-oneself, man’s material externalization, has now become the act
of alienation – i.e., alienation through selling [Verausserung]. This political economy, therefore, starts out by seeming to recognize man, his independence, his spontaneous activity, etc. Since it transfers private property into the very being of man, it can no longer be conditioned by local or national features of private property as something existing outside it. It (political economy) develops a cosmopolitan, universal energy which breaks through every limitation and bond and sets itself up as the only policy, the only universality, the only limitation, and the only bond.
Karl Marx. Economic and Philosophical Manuscripts. Third Manuscript. Private Property and Labor. page XXXVI. 1844.