On this road, which leads to truth past so many errors, the last stage is the hypothesis set up by the so-called Historical School of political economy--the hypothesis, namely, that there exists in the nature of things a gulf between economic theory and practice, which makes it quite conceivable that the principles that are correct _in thesi_ do not coincide with the real course of industrial life. The existence of the problem is thereby more fully established than ever, but its solution is placed outside of the domain of theoretical cognisance. For the Historical School is perfectly correct in maintaining that the abstractions of the current economic doctrine are practically useless, and that this is true not only of some of them, but of all. The real human economy does _not_ obey those laws which the theorists have abstractedly deduced from economic phenomena. Hence it is only possible either that the human economy is by its very nature unfitted to become the object of scientific abstraction and cognisance, or that the abstractions hitherto made have been erroneous--erroneous, that is, not in the sense of being actually out of harmony with phenomena from which they are correctly and logically deduced, but in the sense of being theoretically erroneous, deduced according to wrong principles, and therefore useless both _in abstracto_ and _in concreto_. Of these alternatives only the second can, in reality, be correct. There is absolutely no reasonable ground for supposing that the laws which regulate the economic activity of men should be beyond human cognisance; and still less ground is there for assuming that such laws do not exist at all. We must therefore suppose that the science which seeks to discover these laws has hitherto failed to attain its object simply because it has been upon the wrong road--that is, that the principles of political economy are erroneous because, in deducing them from the economic phenomena, some fact has been overlooked, some mistake in reasoning has been committed. There _must_ be a correct solution of the problem of political economy; and the solution of the social problem derived from the theory of social evolution offers at once the key to the other.