And the same criticism is applicable to the other argument before us, which admits that a man who invents a productive machine, or who writes a remunerative play, is, so long as he lives, entitled, because he is the true producer of them, to certain profits arising from the use of either; but adds that his rights to such profits end with his own life, and lose all sanction in justice the moment they are transferred to an heir. In the heir's hands, it is urged, they entirely change their character, and, instead of enabling a man to secure what is honestly his own, become means by which he is enabled to steal what morally belongs to others.
Now, if it is seriously contended that nobody has a right to anything which at some time or other he has not personally produced, the interest on machinery, as soon as the inventor dies, not only ought not to belong to the inventor's heir, but it ought not to belong to anybody; for if this interest is not produced by the heir, it is certainly not produced by any of the heir's contemporaries. A contention like this is absurd; there must therefore be something amiss with the premises which lead up to it. Socialists who admit that an inventor during his lifetime has a right to the interest resulting from the use of his own inventions, endeavour to solve the difficulty by maintaining that after his death both invention and interest should pass into the hands of the state; but this doctrine, on whatever grounds it may be defended, cannot be defended as based on the principle now in question, that the sole valid title to possession is personal production. It must, if it is based on any abstract moral principle at all, be based on one of a much more general kind, according to which the ultimate standard of justice is not the deeds of the individual, but the general welfare of society.
Here it is true that the appeal is still to abstract justice, but it is not an appeal to abstract justice only. In order to condemn interest on any such ground as this, it is necessary to assume or prove that to make interest illegal, or to confiscate it by taxation when it arises, or by any other means to render its enjoyment impossible, will as a matter of fact have the result desired--namely, a permanent rise in the general level of prosperity. It is only by means of an assumption of this purely practical kind that the abstract moral principle can be applied to the case at all; and thus let us approach the problem from whatever side we will, we are brought from the region of theory down into that of practice, not, indeed, by an abrupt leap, but by a gradual and necessary transition. We are not abandoning our considerations of what, in abstract justice, ought to be; but we are compelled to interpret what ought to be by considerations of what, as the result of such and such arrangements, will be.