Introduction, Chapter 3, Footnote #06
Aversion to Labour
It may perhaps be urged that an aversion to labour must at any rate be supposed to operate at the point at which the labourer leaves off; since otherwise he would not leave off, provided he could obtain any object of desire by continuing to work. And, no doubt, it would be usually safe to infer that at the close of any worker's daily task of paid labour he likes such labour decidedly less than some other unremunerated employment of his time. Still the argument is not conclusive: for a man may cease to labour merely because it would be bad economy of his powers to continue, since additional work to-day would cause a more than proportionate decrease in efficiency for work hereafter. I suppose that this explanation would be frequently true, as regards the higher kinds of intellectual work.