It finally dawned upon the leaders of thought in the Fatherland, as it had but shortly before dawned upon philosophers and men of science in other lands, that the reputed sexual difference in intelligence was not due to difference in brain size or brain structure, or innate power of intellect, but rather to some other factors which had been neglected, or overlooked, as being unessential or of minor importance. These factors, on further investigation, proved to be education and opportunity. As far back as 1869 that keen observer and philosopher, John Stuart Mill, had expressed himself on the subject in the following words: "Like the French compared with the English, the Irish with the Swiss, the Greeks or Italians compared with the German races, so women compared with men may be found, on the average, to do the same things with some variety in the particular kind of excellence. But that they would do them fully as well, on the whole, if their education and cultivation were adapted to correcting instead of aggravating the infirmities incident to their temperament, I see not the smallest reason to doubt."[107] It would be difficult to find a better illustration of the sluggishness of the male as compared with the female mind than the tardiness of men of science in arriving at a sane conclusion respecting the subject of this chapter. For five hundred years ago Christine de Pisan arrived at the same conclusion which the learned professors of Germany reached only in the last decade of the nineteenth century. Discussing in _La Cite des Dames_ the question at issue she writes as follows: "I say to thee again, and doubt never the contrary, that if it were the custom to put the little maidens to the school, and they were made to learn the sciences as they do to the men-children, that they should learn as perfectly, and they should be as well entered into the subtleties of all the arts and sciences as men be. And peradventure, there should be more of them, for I have teached heretofore that by how much women have the body more soft than the men have, and less able to do divers things, by so much they have the understanding more sharp there as they apply it." Christine de Pisan's statement is virtually a challenge demanding the same educational opportunities for women as were accorded to men. But it was a challenge that men did not see fit to accept until full five centuries had elapsed, and until it was no longer possible to deny giving satisfaction to the long-aggrieved half of humanity. It was also an appeal to experiment and an appeal, likewise, to the teachings of history in lands where women have enjoyed the same educational advantages as men.