Finally, with regard to the adult: it does occasionally happen even in our rushing times that some one commits a poem to memory with the avowed intention of giving exercise to his mind. Were this practical end the only one, play, indeed, would not be involved; but, as a rule, pleasure in acquisition as such is combined with the other motive. Such exercise was formerly much more common, and at a time when few could read surprising feats were performed. A survival of this may be found now in the Balkan countries, where the heroic songs are still orally preserved. In mental exercise of this kind it is difficult to draw the line between the emotions aroused by the content of the piece and what pleasure is derived from the act of learning, and we will not here go into that phase of the subject, only mentioning, in closing the section, that conjuring up one’s own past is another form of memory-play with the feelings. 2. _Imagination_ The phenomena which the exigencies of language compel us to include under the words imagination or fantasy naturally fall into two quite clearly differentiated groups, namely, illusion, either playful or serious, and the voluntary or involuntary transformation of our mental content. Considerable controversy has arisen as to which of these groups shall be taken as the basis of a definition, and it is in opposition to the prevailing view that I have designated the capacity for illusion as my choice for that purpose. Yet on reflection I consider it more prudent not to attempt a comprehensive definition, but rather to keep separate the two distinct departments of mental life which the usages of language too closely associate, and which, while they are closely interwoven in some of their aspects, are yet of so heterogeneous a character that we may hope to distinguish between them in all essentials. (_a_) Playful Illusion