What relation, then, do these two explanations {93} bear to each other? In a direct way they are not related at all. They neither conflict with each other nor overlap each other. They are both of them true; but true as explaining different sets of phenomena. One of the great errors of which our modern sociologists are guilty consists in their failure to perceive that social progress is not a single movement but the joint result of two, which differ from each other—to repeat what was said just now—quite as much as do the two movements of the earth. The difference between them will become instantly clear to us if we will turn our attention merely to the single obvious fact that the two take place at different rates of speed, the one set of changes being slow, like the succession of years; the other set of changes being rapid, like the succession of days. The general rise in capacity which distinguishes the modern civilised nations from primitive man, or from the lowest savages of to-day, and which has been due to what Mr. Kidd calls “_the preponderating reproduction of individuals slightly above the average_,” has been the work of an incalculable number of centuries. It has been so slow that, in many respects at all events, it has been indistinguishable during the course of several thousand years. The great thinkers amongst the ancient Egyptians were not congenitally inferior to the great thinkers of to-day. The brain of Aristotle was equal to the brain of Newton; whilst the masons whose hands constructed the Coliseum and the Parthenon knew as much of their craft as those who {94} constructed the Imperial Institute. But with this slowness in the rise of the general level of capacity let us compare the progressive results achieved within some short period. We cannot do better than take the past hundred years, and consider the progress made in the material arts of life. How the whole spectacle changes! Within that short period, at all events, no one will venture to maintain that the average congenital capacities of our own countrymen have been enlarged. We are not wittier than Horace Walpole, more polite than Lord Chesterfield, more shrewd and sensible than Dr. Johnson; whilst it is easy to see by reference to those trades, such as the building trade, which science and invention have done comparatively little to alter, that the natural efficiency of the average workman is no greater now than in the days of our great-great-grandfathers. And yet during that short period what an astounding progress has taken place! To sum it up in a bald economic formula, whilst the capacities of the average Englishman have remained altogether stationary, the economic productivity per head of the population of this country has during the past century trebled, and more than trebled itself.