=The Scientific Spirit.=--The older standards were embodied in religious and political ideas and institutions; the agency which was to disentangle and bring into clear consciousness the standards _as such_, was the scientific spirit, the knowledge and reflection of an intellectual people at a period of extraordinarily rapid development. The commercial life, the free intercourse with other peoples and civilizations, especially in the colonies, the absence of any generally dominating political authority, the architectural problems suggested by a beauty-loving people,--all promoted alertness and flexibility of mind. In a concrete form, this rational character had already found expression in the quality of Greek art. Reference has already been made to the formal side of Greek art, with its embodiment of rhythm and measure; the subject-matter shows the same element. The Greek world, as contrasted with the barbarian world, was conceived by the Greek as the realm of light contrasted with darkness; the national God, Apollo, embodied this ideal of light and reason, and his fitting symbol was the sun. The great Pan-Athenaic procession, as reproduced in the Parthenon frieze, celebrated the triumph of Greek light and intelligence over barbarian darkness. Athena, goddess of wisdom, was a fitting guardian of the most Greek of all Greek cities. Greek tragedy, beginning in hymns of worship, soon passed over into a portrayal of the all-controlling laws of life, as these are brought into stronger relief by a tragic collision with human agents. It was, however, in the realm of science that this intellectual genius found field for expression in a clearly conscious manner. Almost all our sciences were originated by the Greeks, and they were particularly successful in those which called for abstract thinking in the highest degree. Euclid's geometry and Aristotle's logic are conspicuous illustrations of this ability. The most general conceptions of natural science: e.g., the conception of the atom and the whole materialistic theory of the universe; the conception of evolution, meaning by this the process of change according to an all-controlling law; the conception of natural selection, according to which those organisms survive which are fitted for their environment,--all these were the product of the keen intelligence of the Greeks. Nor was their scientific ability expended upon external nature alone. The conception of history as more than a series of events, the comparative method in the study of political systems, the analysis of literary and artistic effects, attest the same clarity of mind and the same eager search for the most general laws of every aspect of experience.