An instinctive recognition of this necessity kept Greek mythology ever ready to return to Nature to gather its materials afresh from a docile, if poetical, observation of reality. The character of the god must be studied in the manifestations of his chosen element; otherwise men might forget that, although the form of the god was poetical, his essence was a positive reality of the most practical kind. Zeus must still toss his ambrosial locks with a certain irritation, in order that we may recognize him in the rumblings of the sky; he must still be capable of wrath and deliberate malice, that his awful hand may be thought to have hurled the thunderbolt. Cronos must not be forbidden to devour his children, else we should no longer reverence in him the inexorable might of time. Mythology was quite right in not shrinking from such poetic audacities. They were its chief title to legitimacy, the proof, amid the embroideries of fancy which over-lay the divine idea, that the god was not an invention, but a fact. He had been found, he was known. His character, like all character, was merely a principle which reflection discovered in his observed conduct. The reality, then, of the mythological gods was initially unquestionable; and the more faithful the study of Nature by which the poet was inspired, the more authority did his prophetic vision retain. But the intense imaginative vitality that must have preceded Homer and Hesiod, the prodigious gift of sympathetic observation to which we owe Zeus and Pan and all their endless retinue, was too glorious to last. No later interpreter could find so much meaning in his text. Mythology was accordingly placed in a sad dilemma, with either horn fatal to its life; it must either be impoverished to remain sincere, or become artificial to remain adequate. The history of Greek religion, on its speculative side, is nothing but the story of this double decadence. Reflection upon the process of Nature and desire for philosophic truth led inevitably to a blank pantheism and to the reduction of positive traditions to moral allegories. This was the direction taken by the Stoic theology. On the other hand, adherence to the traditional gods, with no further vivifying reference to their natural functions in the world, could lead only to arbitrary fictions, which, having no foothold or justification in reality, were incapable of withstanding the first sceptical attack. What an age of imagination had intuited as truth, an age of reflection could preserve only as fable; and as fable, accordingly, the religion of the ancients survived throughout the Christian ages. It remains still the mother-tongue of the imagination and, in spite of all revolutions and admixtures, is the classic language of art and poetry, which no other means of expression has superseded.