Read it through once

Why is it that, as Disraeli has pointed out, civilization, culture, science, and religion had their origins in the desert? The answer is not difficult to see: for there is a dry, healthy climate; the severe strain of a long day's journey is varied by enforced leisure, when, resting at his tent-door, the Arab is irresistibly compelled to study the stars and to contemplate the infinite beauty of the night. It seems also to have been in the desert of the old world that man first learnt to cultivate the soil. In fact, it was only by irrigation on great tracts of alluvium, such as were furnished by the Nile and Euphrates, that the enormous populations of Egypt, Babylon, Nineveh, and the other great monarchies could be maintained. So that city life on a big scale first developed there.