After the decline of Nature-worship, and when through the constantly increasing power gained by the ruder elements in human society a knowledge of the scientific principles underlying ancient religion had been partially lost or forgotten, it became necessary for philosophers to conceal the original conception of the Deity and to clothe their sacred writings in allegory. Hence it is observed that every ancient form of religion has a cabala containing its secret doctrines--doctrines the inner meaning of which was known only to the few. In order that these truths might be preserved, they were inscribed on the leaves of trees in characters or symbols understood only by the initiated. The allegories beneath which these higher truths were concealed were handed down as traditions to succeeding generations--traditions in which history, astrology, and mythology are strangely combined. After long periods, through war, conquest, and the various changes incidental to shifting environment, these traditions were in the main forgotten. Fragments of them, however, were from time to time gathered together, and, intermingled with later doctrines, were used by the priests as a means of increased self-aggrandizement and power. It is now thought that the Iliad (Rhapsodies) of Homer is only a number of "detached songs" which perhaps for centuries were delivered orally, and that they contain the secret doctrines of the priests. Porphyry says that "we ought not to doubt that Homer has secretly represented the images of divine things under the concealment of fable." It has been said of Plato that he banished the poems of Homer from his imaginary republic for the reason that the people might not be able to distinguish what is from what is not allegorical. Hippolytus informs us that the Simonists declared that in Helen resided the principle of intelligence; "and thus, when all the powers were for claiming her for themselves, sedition and war arose, during which this chief power was manifested to nations." These songs which were gathered together by Pisistratus and revised by Aristotle for the use of Alexander, have generally been regarded merely as a bit of history recounting a severe and protracted struggle between the Greeks and Trojans. Within the earliest historical accounts which we have of the Egyptians, we observe that their ceremonies and symbols have already become multitudinous, the true meaning of the latter being concealed. The masses of the people, who had grown too sensualized and ignorant to receive the higher divine "mysteries," and too gross to be entrusted with their true significance, had become idolaters.