Plutarch’s faith and interest in oracles in general and in the Delphian oracle of Apollo in particular are attested by three of his essays, the _De defectu oraculorum_, _De Pythiae oraculis_ and _De Ei apud Delphos_. At the same time these essays attest the decline of the oracles from their earlier popularity and greatness. The oracular cave of Trophonius, of which we shall hear again in the _Life of Apollonius of Tyana_, also comes into Plutarch’s works, and the prophetic and apocalyptic vision is described of a youth who spent two nights and a day there in an endeavor to learn the nature of the demon of Socrates.[924] [Sidenote: Divination justified.] Plutarch further had faith in divination in general, whether by dreams, sneezes or other omens: but he attempted to give a dignified philosophical and theological explanation of it. Few men receive direct divine revelation, in his opinion, but to many signs are given on which divination may be based.[925] He held that the human soul had a natural faculty of divination which might be exercised at favorable times and when the bodily state was not unfavorable.[926] A speaker in one of his dialogues justifies divination even from sneezes and like trivial occurrences upon the ground that as the faint beat of the pulse has meaning for the physician and a small cloud in the sky is for a skilful pilot a sign of impending storm, so the least thing may be a clue to the truly prophetic soul.[927] The extent of Plutarch’s faith in dreams may be inferred from his discussion of the problem, Why are dreams in autumn the least reliable?[928] First there is Aristotle’s suggestion that eating autumn fruit so disturbs the digestion that the soul is left little opportunity to exercise its prophetic faculty undistracted. If we accept the doctrine of Democritus that dreams are caused by images from other bodies and even minds or souls, which enter the body of the sleeper through the open pores and affect the mind, revealing to it the present passions and future designs of others,—if we accept this theory, it may be that the falling leaves in autumn disturb the air and ruffle these extremely thin and film-like emanations. A third explanation offered is that in the declining months of the year all our faculties, including that of natural divination, are in a state of decline. In the case of oracles like that at Delphi it is suggested that the Pythia’s natural faculty of divination is stimulated by “the prophetical exhalations from the earth” which induce a bodily state favorable to divination.[929] The god or demon, however, is the underlying and directing cause of the oracle.[930] [Sidenote: Demons as mediators between gods and men.]