"The will of the capitalist is certainly to take as much as possible. What we have to do is not to talk about his will, but to enquire about his power, the limits of that power, and the character of those limits."

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What the working man sells is not directly his Labor, but his Laboring Power, the temporary disposal of which he makes over to the capitalist. This is so much the case that I do not know whether by the English Law, but certainly by some Continental Laws, the maximum time is fixed for which a man is allowed to sell his laboring power. If allowed to do so for any indefinite period whatever, slavery would be immediately restored. Such a sale, if it comprised his lifetime, for example, would make him at once the lifelong slave of his employer.

— Karl Marx