Representation, of course, depends upon the preceding phases of Memory known as Impression, Retention and Recollection. Unless the Impression is clear; unless the Retention is normal, there can be no Representation. And unless one _recollects_ there can be no Representation. Recollection (which is really a re-collection of percepts) must precede Representation in the shape of mental images or pictures. Recollection re-collects the mental materials out of which the image is to be constructed. But, as Brooks says: "It is not to be assumed that knowledge is retained as a picture; but that it is _recreated_ in the form of a picture or some other mental product when it is recalled." The process is analogous to the transmutation of the sound-waves entering the receiver of a telephone, into electrical-waves which are transmitted to the receiver, where they are in turn re-transmuted to sound-waves which enter the ear of the listener. It will be seen at once that there is the closest possible relation between the processes of Representation and those of Memory--in fact, it is quite difficult to draw a clear line of division between them. Some make the distinction that Representation furnishes us with an exact reproduction of _the past_; while Imagination combines our mental images into _new products_. That is, Representation merely _reproduces_; while Imagination _creates_ by forming new combinations; or Representation deals with a reproduction of the Actual; while Imagination deals with the Ideal. Wundt speaking of this difficult distinction says: "Psychologists are accustomed to define _memory images_ as ideas which _exactly reproduce_ some previous perception, and _fancy images_ as ideas consisting of a combination of elements taken from a whole number of perceptions. Now memory images in the sense of this definition simply do not exist.... Try, for instance, to draw from memory some landscape picture which you have only once seen, and then compare your copy with the original. You will expect to find plenty of mistakes and omissions; but you will also invariably find that you have put in a great deal which was not in the original, but which comes from landscape pictures which you have seen somewhere else." While we generally speak of Representation _picturing_ the recollected percepts, still, we must not make the mistake of supposing that it is concerned with, or limited to, only mental pictures. We are able to _represent_ not only visual percepts but also sounds, smells, tastes or feelings, often so vividly that they appear as almost actually existent. We may also even _represent_, symbolically the processes of reasoning, mathematical operations, etc. In short nearly, if not all experiences which are possible in Presentation are also possible in Representation.