The subject of association naturally conducts us to the second great problem in the theory of dreams—­the explanation of the order in which the various images group themselves in all our more elaborate dreams.

Coherence of Dreams.

A fully developed dream is a complex of many distinct illusory sense-presentations:  in this respect it differs from the illusions of normal waking life, which are for the most part single and isolated.  And this complex of quasi-presentations appears somehow or other to fall together into one whole scene or series of events, which, though it may be very incongruous and absurdly impossible from a waking point of view, nevertheless makes a single object for the dreamer’s internal vision, and has a certain degree of artistic unity.  This plastic force, which selects and binds together our unconnected dream-images, has frequently been referred to as a mysterious spiritual faculty, under the name of “creative fancy.”  Thus Cudworth remarks, in his Treatise concerning Eternal and Immutable Morality:  “That dreams are many times begotten by the phantastical power of the soul itself ... is evident from the orderly connection and coherence of imaginations which many times are continued in a long chain or series.”  One may find a good deal of mystical writing on the nature and activity of this faculty, especially in German literature.  The explanation of this element of organic unity in dreams is, it may be safely said, the crux in the science of dreams.  That the laws of psychology help us to understand the sequences of dream-images, we have seen.  What we have now to ask is whether these laws throw any light on the orderly grouping of the elements so brought up in consciousness in the form of a connected experience.

It is to be remarked at the outset that a singular kind of unity is sometimes given to our dream-combinations by a total or partial coalescence of different images.  The conditions of such coalescence have been referred to already.[93] Simultaneous impressions or images will always tend to coalesce with a force which varies directly as the degree of their similarity.  Sometimes this coalescence is instantaneous and not made known to consciousness.  Thus, Radestock suggests that if the mind of the sleeper is simultaneously invaded by an unpleasant sensation arising out of some disturbance of the functions of the skin, and a subjective visual sensation, the resulting mental image may be a combination of the two, under the form of a caterpillar creeping over the bodily surface.  And the coalescence may even be prepared by sub-conscious operations of waking imagination.  Thus, for example, I once spoke about the cheapness of hares to a member of my family, who somewhat grimly suggested that they were London cats.  I did not dwell on the idea, but the following night I dreamt that I saw a big hybrid creature, half hare, half cat, sniffing about a cottage.  As it stood on its hind legs and took a piece of food from a window-ledge, I became sure that it was a cat.  Here it is plain that the cynical observation of my relative had, at the moment, partially excited an image of this feline hare.  In some dreams, again, we may become aware of the process of coalescence, as when persons who at one moment were seen to be distinct appear to our dream-fancy to run together in some third person.