WE have found by observation that the most stimulating challenge is one of mean degree between an excess of severity and a deficiency of it, since a deficient challenge may fail to stimulate the challenged party at all, while an excessive challenge may break his spirit. But what about the challenge with which he is just capable of coping ? On a short view this is the most stimulating challenge imaginable; and, in the concrete instances of the Polynesians and the Eskimos and the Nomads and the 'Osmanlis and the Spartans, we have observed that such challenges are apt to evoke tours de force. We have also observed, however, that in the next chapter of the story these tours de force exact, from those who have performed them, a fatal penalty in the shape of an arrest in their development. Therefore, on the longer view, we must pronounce that the evocation of the greatest immediate response is not the ultimate test of whether any given challenge is the optimum from the standpoint of evoking the greatest response on the whole and in the end. The real optimum challenge is one which not only stimulates the challenged party to achieve a single successful response but also stimulates him to acquire momentum that carries him a step farther: from achievement to a fresh struggle, from the solution of one problem to the presentation of another, from Yin to Yang again. The single finite movement from a disturbance to a restoration of equilibrium is not enough if genesis is to be followed by growth. And, to convert the movement into a repetitive, recurrent rhythm, there must be an élan vital (to use Bergson's term) which carries the challenged party through equilibrium into an overbalance which exposes him to a fresh challenge and thereby inspires him to make a fresh response in the form of a further equilibrium ending in a further overbalance, and so on in a progression which is potentially infinite.
This élan, working through a series of overbalances, can be detected in the course of the Hellenic Civilization from its genesis up to its zenith in the fifth century B.C.
The first challenge presented to the new-born Hellenic Civilization was the challenge of chaos and ancient night. The disintegration of the apparented Minoan Society had left a welter of social debris—marooned Minoans and stranded Achaeans and Dorians. Would the sediment of an old civilization be buried under the