The very word mystery, according to Demetrius Phalereus, was a metaphorical expression that denoted the secret awe which darkness and gloom inspired. The night was almost always the time fixed for their celebration; and they were ordinarily termed nocturnal ceremonies. Initiations into the Mysteries of Samothrace took place at night; as did those of Isis, of which Apuleius speaks. Euripides makes Bacchus say, that his Mysteries were celebrated at night, because there is in night something august and imposing.

Nothing excites men's curiosity so much as Mystery, concealing things which they desire to know: and nothing so much increases curiosity as obstacles that interpose to prevent them from indulging in the gratification of their desires. Of this the Legislators and Hierophants took advantage, to attract the people to their sanctuaries, and to induce them to seek to obtain lessons from which they would perhaps have turned away with indifference, if they had been pressed upon them. In this spirit of mystery they professed to imitate the Deity, who hides Himself from our senses, and conceals from us the springs by which He moves the Universe. They admitted that they concealed the highest truths under the veil of allegory, the more to excite the curiosity of men, and to urge them to investigation. The secrecy in which they buried their Mysteries, had that end. Those to whom they were confided, bound themselves, by the most fearful oaths, never to reveal them. They were not allowed even to speak of these important secrets with any others than the initiated; and the penalty of death was pronounced against any one indiscreet enough to reveal them, or found in the Temple without being an Initiate; and any one who had betrayed those secrets, was avoided by all, as excommunicated.

Aristotle was accused of impiety, by the Hierophant Eurymedon, for having sacrificed to the manés of his wife, according to the rite used in the worship of Ceres. He was compelled to flee to Chalcis; and to purge his memory from this stain, he directed, by his will, the erection of a Statue to that Goddess. Socrates, dying, sacrificed to Esculapius, to exculpate himself from the suspicion of Atheism. A price was set on the head of Diagoras, because he had divulged the Secret of the Mysteries. Andocides was accused of the same crime, as was Alcibiades, and both were cited to answer the charge before the inquisition at Athens, where the People were the Judges. Æschylus the Tragedian was accused of having represented the Mysteries on the stage; and was acquitted only on proving that he had never been initiated.

Seneca, comparing Philosophy to initiation, says that the most sacred ceremonies could be known to the adepts alone: but that many of their precepts were known even to the Profane. Such was the case with the doctrine of a future life, and a state of rewards and punishments beyond the grave. The ancient legislators clothed this doctrine in the pomp of a mysterious ceremony, in mystic words and magical representations, to impress upon the mind the truths they taught, by the strong influence of such scenic displays upon the senses and imagination.

In the same way they taught the origin of the soul, its fall to the earth past the spheres and through the elements, and its final return to the place of its origin, when, during the continuance of its union with earthly matter, the sacred fire, which formed its essence, had contracted no stains, and its brightness had not been marred by foreign particles, which, denaturalizing it, weighed it down and delayed its return. These metaphysical ideas, with difficulty comprehended by the mass of the Initiates, were represented by figures, by symbols, and by allegorical analogies; no idea being so abstract that men do not seek to give it expression by, and translate it into, sensible images.

The attraction of Secrecy was enhanced by the difficulty of obtaining admission. Obstacles and suspense redoubled curiosity. Those who aspired to the initiation of the Sun and in the Mysteries of Mithras in Persia, underwent many trials. They commenced by easy tests and arrived by degrees at those that were most cruel, in which the life of the candidate was often endangered. Gregory Nazianzen terms them tortures and mystic punishments. No one can be initiated, says Suidas, until after he has proven, by the most terrible trials, that he possesses a virtuous soul, exempt from the sway of every passion, and at it were impassible. There were twelve principal tests; and some make the number larger.

The trials of the Eleusinian initiations were not so terrible; but they were severe; and the suspense, above all, in which the aspirant was kept for several years [the memory of which is retained in Masonry by the ages of those of the different Degrees], or the interval between admission to the inferior and initiation in the great Mysteries, was a species of torture to the curiosity which it was desired to excite. Thus the Egyptian Priests tried Pythagoras before admitting him to know the secrets of the sacred science. He succeeded, by his incredible patience and the courage with which he surmounted all obstacles, in obtaining admission to their society and receiving their lessons. Among the Jews, the Essenes admitted none among them, until they had passed the tests or several Degrees.

By initiation, those who before were fellow-citizens only, became brothers, connected by a closer bond than before, by mean of a religious fraternity, which, bringing men nearer together united them more strongly: and the weak and the poor could more readily appeal for assistance to the powerful and the wealthy, with whom religious association gave them a closer fellowship.

The Initiate was regarded as the favorite of the Gods. For him alone Heaven opened its treasures. Fortunate during life, he could, by virtue and the favor of Heaven, promise himself after death an eternal felicity.

The Priests of the Island of Samothrace promised favorable winds and prosperous voyages to those who were initiated. It was promised them that the CABIRI, and Castor and Pollux, the DIOSCURI, should appear to them when the storm raged, and give them calms and smooth seas: and the Scholiast of Aristophanes says that those initiated in the Mysteries there were just men, who were privileged to escape from great evils and tempests.