The study of psychology proves that hallucinations, or illusions, may exist in man without the intellect being disordered. In some instances, they can be produced, by effort of the will. Dr. Wigan, in his able work, _Duality of the Mind_, relates:--"A painter who succeeded to a large portion of the practice, and (as he thought) to more than all the talent of Sir Joshua Reynolds, was so extensively employed, that he informed me he had once painted (large and small) three hundred portraits in one year. This would seem physically impossible, but the secret of his rapidity and of his astonishing success was this: He required but one sitting, and painted with miraculous facility. I myself saw him execute a Kit-Kat portrait of a gentleman well known to me in little more than eight hours; it was minutely finished, and a most striking likeness. On asking him to explain it, he said, 'When a sitter came, I looked at him attentively for half-an-hour, sketching from time to time on the canvas. I wanted no more--I put away my canvas, and took another sitter. When I wished to resume my first portrait, _I took the man and sat him in the chair, where I saw him as distinctly as if he had been before me in his own proper person_--I may almost say more vividly. I looked from time to time at the imaginary figure, then worked with my pencil, then referred to the countenance, and so on, just as I should have done had the sitter been there. _When I looked at the chair, I saw the man!_ This made me very popular; and, as I always succeeded in the likeness, people were very glad to be spared the tedious sittings of other painters. I gained a great deal of money, and was very careful of it. Well for me and my children that it was so. Gradually I began to lose the distinction between the imaginary figure and the real person, and sometimes disputed with sitters that they had been with me the day before. At last I was sure of it, and then--and then--all is confusion. I suppose they took the alarm. I recollect nothing more--I lost my senses--was thirty years in an asylum. The whole period, except the last six months of my confinement, is a dead blank in my memory, though sometimes, when people describe their visits, I have a sort of imperfect remembrance of them; but I must not dwell on these subjects.'" It is an extraordinary fact that, when this gentleman resumed his pencil, after a lapse of thirty years, he painted nearly as well as when insanity compelled him to discontinue it. His imagination was still exceedingly vivid, as was proved by a portrait, for he had only two sittings of half-an-hour each; the latter solely for the dress and for the _eyebrows_, which he could not fix in his memory. It was found that the excitement threatened danger, and he was persuaded to discontinue the exercise of his art. He lived but a short time afterwards.