We have seen that there are two cases of memory; that in which sensations are remembered, and that in which ideas. It is said, that there are men, who, by often telling a mendacious story as true, come at last to believe it to be true. When this happens, the fact is, that a case of the memory of _ideas_, comes to be mistaken for a case of the memory of _sensations_. How did the man know at first that it was a fictitious story; and how did he afterwards lose that knowledge? He knew, at first, by certain associations; he lost his knowledge, by losing those associations, and {334} acquiring others in their stead. When he first told the story, the circumstances related called up to turn the idea of himself fabricating the story. This was the memory of the fabrication. In repeating the story as real, the idea of himself fabricating the story is hurried over rapidly; the idea of himself as actor in the story is dwelt upon with great emphasis. In continued repetitions, the first circumstance being attended to as little as possible, the association of it grows weaker and weaker; the other circumstance engrossing the attention, the association of it grows stronger and stronger; till the weaker is at last wholly overpowered by the stronger, and ceases to have any effect. In delirium, madness, and dreams, men believe that what they only imagine, they hear, see, and do. This so far agrees with the case of forgetfulness, just explained, that, in both, there is a mistake of ideas for sensations; but, in the case of memory, it is a mistake of past ideas for past sensations; in delirium, madness, and dreaming, it is a mistake of present ideas for present sensations.