between the attacked State and others; and the physical conditions prevented any State save Macedonia from becoming overwhelmingly strong. To these conditions, then, we always return, not as to sole causes, but as to determinants. (_d_) In Egypt, again, culture was never deeply disseminated, and before Alexander was hardly at all fecundated by outside contact. In Greece there was always the great uncultured slave substratum; and the arrest of freedom, to say nothing of social ignorance, female subjection, and sexual perversion, ultimately kept vital culture stationary. In Rome, militarism and the multiplication of the slave class, along with the deletion of the independent and industrious middle class, made progressive culture impossible, as surely as it broke down self-government. In all cases alike, over-population, not being met by science, either bred poverty or was obviated by crime and vice. The so-called regeneration of Europe by the barbarian conquest, finally, was simply the beginning of a long period of corrupted and internecine barbarism, the old culture remaining latent; and not till after many centuries did the maturing barbaric civilisation in times of compulsory peace reach the capacity of being fecundated by the intelligent assimilation of the old. But after the Renaissance, as before, the diseases of militarism and class privilege and the political subjection caused a backthrow and intellectual stagnation, which was assisted by the commercial decline brought upon Italy; so that in the feudal period, in one State after another, we have the symptoms of, as it were, senile "decay" and retrogression.[153] In all cases this is to be set down proximately to the deficit of new ideas, and in some to excess of strife, which exhausted spare energy among the leisured class, deepened the misery of the toilers, and normally prevented the intelligent intercourse of peoples. It is become a commonplace of historical philosophy that the Crusades wrought for good inasmuch as they meant fresh communication between East and West. Yet it may be doubted whether much more was not done through the quiet contacts of peace between Saracen and Christian in Western Europe, and by the commerce with the East which preceded the Crusades,[154] than by the forced intercourse following on religious war. In any case, the transition from quasi-decay to progress in Christendom is clearly due to the entrance of new ideas of many species from many directions into the common stock; Greek letters, Saracen physics, and new geographical discovery all combining to generate thought.