upon Labour an effect exactly opposite to that which was produced on it by such inventions as the primæval plough. Instead of making Labour more efficacious in itself, they make it less and less efficacious, unless it is assisted by Ability. [Sidenote ◆1 They do not become, as is vulgarly said, common property. They belong to those who can use them;] [Sidenote ◆2 And more and more is living Ability required to maintain and use the powers left to it by the Ability of the past.] ◆¹ And here we have the answer to the real argument which lies at the bottom of my American correspondent’s letter—an argument which, in some such words as the following, is to be found repeated in every Socialistic treatise: “When once an invention is made, it becomes common property.” So it does in a certain theoretical sense; but only in the sense in which a knowledge of Chinese becomes common property in England on the publication of a Chinese grammar. For all practical purposes, such a statement is about as true as to say that because anybody can buy a book on military tactics, everybody is possessed of the genius of the Duke of Wellington. ◆² The real truth is, that to utilise modern inventions, and to maintain the conditions of industry which these inventions subserve, as much Ability is required as was required to invent them; though, as I shall have occasion to point out later on, the Ability is of a different kind. [Sidenote ◆1 We must, then, here note that when Ability is said to produce so much of the national income, what is meant is the Ability of men alive at the time,]