The other source of what may, by analogy with the hallucinations of sense, be called the peripherally originating spectra of memory is waking imagination.  In certain morbid conditions of mind, and in the case of the few healthy minds endowed with special imaginative force, the products of this mental activity, may, as we saw when dealing with illusions of perception, closely resemble dreams in their vividness and apparent actuality.  When this is the case, illusions of memory may arise at once just as in the case of dreams.  This will happen more easily when the imagination has for some time been occupied with the same group of ideal scenes, persons, or events.  To Dickens, as is well known, his fictitious characters were for the time realities, and after he had finished his story their forms and their doings lingered with him, assuming the aspect of personal recollections.  So, too, the energetic activity of imagination which accompanies a deep and absorbing sympathy with another’s painful experiences, may easily result in so vivid a realization of all their details as to leave an after-sense of personal suffering.  All highly sympathetic persons who have closely accompanied beloved friends through a great sorrow have known something of this subsequent feeling.

The close connection and continuity between normal and abnormal states of mind is illustrated in the fact that in insanity the illusion of taking past imaginations for past realities becomes far more powerful and persistent.  Abercrombie (Intellectual Powers, Part III. sec. iv.  Sec. 2, “Insanity”) speaks of “visions of the imagination which have formerly been indulged in of that kind which we call waking dreams or castle-building recurring to the mind in this condition, and now believed to have a real existence.”  Thus, for example, one patient believed in the reality of the good luck previously predicted by a fortune-teller.  Other writers on mental disease observe that it is a common thing for the monomaniac to cherish the delusion that he has actually gained the object of some previous ambition, or is undergoing some previously dreaded calamity.

Nor is it necessary to these illusions of memory that there should be any exceptional force of imagination.  A fairly vivid representation to ourselves of anything, whether real or fictitious, communicated by others, will often result in something very like a personal recollection.  In the case of works of history and fiction, which adopt the narrative tense, this tendency to a subsequent illusion of memory is strengthened by the disposition of the mind at the moment of reading to project itself backwards as in an act of recollection.  This is a point which will be further dealt with in the next chapter.