This spirit of innovation and discussion, which made the characteristic of the Greeks, is noted by Diodorus.

"Unlike the Chaldaeans," he observes, "with whom philosophy is delivered from sire to son, and all other employment rejected by its cultivators, the Greeks come late to the science--take it up for a short time--desert it for a more active means of subsistence--and the few who surrender themselves wholly to it practise for gain, innovate the most important doctrines, pay no reverence to those that went before, create new sects, establish new theorems, and, by perpetual contradictions, entail perpetual doubts." Those contradictions and those doubts made precisely the reason why the Greeks became the tutors of the world! There is another characteristic of the Greeks indicated by this remark of Diodorus.

Their early philosophers, not being exempted from other employments, were not the mere dreamers of the closet and the cell.
They were active, practical, stirring men of the world.

They were politicians and moralists as well as philosophers.

The practical pervaded the ideal, and was, in fact, the salt that preserved it from decay.