This, omitting many technical details, and much that is matter of more dispute than common, is a statement, rough, and as popular as possible, of the ideas expressed in Mr. Gurney’s remarkable essay on hallucinations. {186} Here, then, we have a rude working notion of various ways in which hallucinations may be produced.  But there are many degrees in being hallucinated, or enphantosme, as the old French has it.  If we are interested in the most popular kind of hallucinations, ghosts and wraiths, we first discard like Le Loyer, the evidence of many kinds of witnesses, diversely but undeniably hallucinated.  A man whose eyes are so vicious as habitually to give him false information is not accepted as a witness, nor a man whose brain is drugged with alcohol, nor a man whose ‘central terminus’ is abandoned to religious excitement, to remorse, to grief, to anxiety, to an apprehension of secret enemies, nor even to a habit of being hallucinated, though, like Nicolai, he knows that his visionary friends are unreal.  Thus we would not listen credulously to a ghost story out of his own experience from a man whose eyes were untrustworthy, nor from a short-sighted man who had recognised a dead or dying friend on the street, nor from a drunkard.  A tale of a vision of a religious character from Pascal, or from a Red Indian boy during his Medicine Fast, or even from a colonel of dragoons who fell at Prestonpans, might be interesting, but would not be evidence for our special purpose.  The ghosts beheld by conscience-stricken murderers, by sorrowing widowers, by spiritualists in dark rooms, haunted by humbugs, or those seen by lunatics, or by children, or by timid people in lonely old houses, or by people who, though sane at the time, go mad twenty years later, or by sane people habitually visionary, these and many other ghosts, we must begin, like Le Loyer, by rejecting.  These witnesses have too much cerebral activity at the wrong time and place.  They start their hallucinations from the external terminus, the unhealthy organ of sense; from the morbid central terminus; or from some dilapidated cerebral station along the line.  But, when we have, in a sane man’s experience, say one hallucination whether that hallucination does, or does not coincide with a crisis in the life, or perhaps with the death of the person who seems to be seen, what are we to think?  Or again, when several witnesses simultaneously have the same hallucination,—­not to be explained as a common misinterpretation of a real object,—­what are we to think?  This is the true question of ghosts and wraiths.  That apparitions, so named by the world, do appear, is certain, just as it is certain that visionary rats appear to drunkards in delirium tremens.  But, as we are only to take the evidence of sane and healthy witnesses, who were neither in anxiety, grief, or other excitement, when they perceived their one hallucination, there seems to be a difference between their hallucinations