Partial darkness, or obscurity, are the most powerful means by which the sight is deceived: night is therefore the proper season for apparitions. Indeed the state of the mind, at that time, prepares it for the admission of these delusions of the imagination. The fear and caution which must be observed in the night; the opportunity it affords for ambuscades and assassinations; depriving us of society, and cutting off many pleasing trains of ideas, which objects in the light never fail to introduce, are all circumstances of terror: and perhaps, on the whole, so much of our happiness depends upon our senses, that the deprivation of any one may be attended with a proportionate degree of horror and uneasiness. The notions entertained by the ancients respecting the _soul_, may receive some illustrations from these principles. In dark, or twilight, the imagination frequently transforms an inanimate body into a human figure; on approaching the same appearance is not to be found: hence they sometimes fancied they saw their ancestors; but not finding the reality, distinguished these illusions by the name of _shades_. Many of these fabulous narrations might originate from _dreams_. There are times of slumber, when we are sensible of being asleep[38]. On this principle, Hobbes has so ingeniously accounted for the spectre which is said to have appeared to Brutus, that we cannot resist the temptation of inserting it in his own words. “We read,” says he, “of M. Brutus, (one that had his life given him by Julius Cæsar, and was also his favourite, and notwithstanding murdered him) that at Philippi, the night before he gave battle to Augustus Cæsar, he saw a fearful apparition, which is commonly related by historians as a vision; but considering the circumstances, one may easily judge it to have been but a short dream. For, sitting in his tent, pensive and troubled with the horror of his rash act, it was not hard for him, slumbering in the cold, to dream of that which most affrighted him; which fear, as by degrees it made him wake, so it must needs make the apparition by degrees to vanish: and having no assurance that he slept, he could have no cause to think it a dream, or any thing but a vision.”—The well-known story told by Clarendon, of the apparition of the Duke of Buckingham’s father, will admit of a similar solution. There was no man in the kingdom so much the subject of conversation as the Duke; and, from the corruptness of his character, he was very likely to fall a sacrifice to the enthusiasm of the times. Sir George Viliers is said to have appeared to the man at midnight—there is therefore the greatest probability that the man was asleep; and the dream affrighting him, made a strong impression, and was likely to be repeated.