Let us make the differences between the two clear by a few simple examples.

Concrete images are: In the visual sphere, the recollection of faces, monuments, landscapes, etc.; in the auditory sphere, the remembrance of the sounds of the sea, wind, the human voice, a melody, etc.; in the motor sphere, the tossings one feels when resting after having been at sea, the illusions of those who have had limbs amputated, etc.

Symbolic images are: In the visual order, written words, ideographic signs, etc.; in the auditory order, spoken words or verbal images; in the motor order, significant gestures, and even better, the finger-language of deaf-mutes.

Psychologically, these two groups are not identical in nature. Concrete images result from a persistence of perceptions and draw from the latter all their validity; symbolic images result from a mental synthesis, from an association of perception and image, or of image and image. If they have not the same origin, no more do they disappear in the same way, as is proven by very numerous examples of aphasia.

The originality of mystic imagination is found in this fact: It transforms concrete images into symbolic images, and uses them as such. It extends this process even to perceptions, so that all manifestations of nature or of human art take on a value as signs or symbols. We shall later find numerous examples of this. Its mode of expression is necessarily synthetic. In itself, and because of the materials that it makes use of, it differs from the affective imagination previously described; it also differs from sensuous imagination, which makes use of forms, movements, colors, as having a value of their own; and from the imagination developing in the functions of words, through an analytic process. It has thus a rather special mark.

Other characters are related to this one of symbolism, or else are derived from it, viz.:

(1) An external character: the manner of writing and of speaking, the mode of expression, whatever it is. "The dominant style among mystics," says von Hartmann, "is metaphorical in the extreme—now flat and ordinary, more often turgid and emphatic. Excess of imagination betrays itself there, ordinarily, in the thought and in the form in which that is rendered.... A sign of mysticism which it has been believed may often be taken as an essential sign, is obscurity and unintelligibility of language. We find it in almost all those who have written."[99] We might add that even in the plastic arts, symbolists and "décadents" have attempted, as far as possible, methods that merely indicate and suggest or hint instead of giving real, definite objects: which fact makes them inaccessible to the greater number of people.

This characteristic of obscurity is due to two causes. First, mystical imagination is guided by the logic of feeling, which is purely subjective, full of leaps, jerks, and gaps. Again, it makes use of the language of images, especially visual images—a language whose ideal is vagueness, just as the ideal of verbal language is precision. All this can be summed up in a phrase—the subjective character inherent in the symbol. While seeming to speak like everyone else, the mystic uses a personal idiom: things becoming symbols at the pleasure of his fancy, he does not use signs that have a fixed and universally admitted value. It is not surprising if we do not understand him.

(2) An extraordinary abuse of analogy and comparison in their various forms (allegory, parable, etc.)—a natural consequence of a mode of thinking that proceeds by means of symbols, not concepts. It has been said, and rightly, that "the only force that makes the vast field of mysticism fruitful is analogy."[100] Bossuet, a great opponent of mystics, had already remarked: "One of the characteristics of these authors is the pushing of allegories to the extreme limit." With warm imagination, having at their disposal overexcited senses, they are lavish of changes of expressions and figures, hoping thereby to explain the world's mysteries. We know to what inventive labors the Vedas, the Bible, the Koran, and other sacred books have given rise. The distinction between literal and figurative sense, which is boundlessly arbitrary, has given commentators a freedom to imagine equal to that of the myth-creators.

All this is yet very reasonable; but the imagination left to itself stops at no extravagance. After having strained the meaning of expressions, the imaginative mind exercises itself on words and letters. Thus, the cabalists would take the first or the last letters of the words composing a verse, and would form with them a new word which was to reveal the hidden meaning. Again, they would substitute for the letters composing words the numbers that these letters represent in the Hebrew numerical system and form the strangest combinations with them. In the Zohar, all the letters of the alphabet come before God, each one begging to be chosen as the creative element of the universe.