“Suppose a clothing manufacturer learns of a machine that will make men’s and women's overcoats for half as much labor as previously. He installs the machines and drops half his labor force.This looks at first glance like a clear loss of employment. But the machine itself required labor to make it; so here, as one offset, are jobs that would not otherwise have existed. The manufacturer, how ever, would have adopted the machine only if it had either made better suits for half as much labor, or had made the same kind of suits at a smaller cost. If we assume the latter, we cannot assume that the amount of labor to make the machines was as great in terms of pay rolls as the amount of labor that the clothing manufacturer hopes to save in the long run by adopting the machine; otherwise there would have been no economy, and he would not have adopted it.So there is still a net loss of employment to be accounted for. But we should at least keep in mind the real possibility that even the first effect of the introduction of labor-saving machinery may be to increase employment on net balance; because it is usually only in the long run that the clothing manufacturer expects to save money by adopting the machine: it may take several years for the machine to "pay for itself."After the machine has produced economies sufficient to offset its cost, the clothing manufacturer has more profits than before. (We shall assume that he merely sells his coats for the same price as his competitors, and makes no effort to undersell them.) At this point, it may seem, labor has suffered a net loss of employment, while it is only the manufacturer, the capitalist, who has gained. But it is precisely out of these extra profits that the subsequent social gains must come. The manufacturer must use these extra profits in at least one of three ways, and possibly he will use part of them in all three: (1) he will use the extra profits to expand his operations by buying more machines to make more coats; or (2) he will invest the extra profits in some other industry; or (3) he will spend the extra profits on increasing his own consumption. Whichever of these three courses he takes, he will increase employment.”

Economics in One Lesson (1946), The Curse of Machinery (ch. 7)