_Degenerates are not always criminals, prostitutes, anarchists, and pronounced lunatics; they are often authors and artists. These, however, manifest the same mental characteristics, and for the most part the same somatic features, as the members of the above-mentioned anthropological family, who satisfy their unhealthy impulses with the knife of the assassin or the bomb of the dynamiter, instead of with pen and pencil._ _Some among these degenerates in literature, music, and painting have in recent years come into extraordinary prominence, and are revered by numerous admirers as creators of a new art, and heralds of the coming centuries._ _This phenomenon is not to be disregarded. Books and works of art exercise a powerful suggestion on the masses. It is from these productions that an age derives its ideals of morality and beauty. If they are absurd and anti-social, they exert a disturbing and corrupting influence on the views of a whole generation. Hence the latter, especially the impressionable youth, easily excited to enthusiasm for all that is strange and seemingly new, must be warned and enlightened as to the real nature of the creations so blindly admired. This warning the ordinary critic does not give. Exclusively literary and æsthetic culture is, moreover, the worst preparation conceivable for a true knowledge of the pathological character of the works of degenerates. The verbose rhetorician exposes with more or less grace, or cleverness, the subjective impressions received from the works he criticises, but is incapable of judging if these works are the productions of a shattered brain, and also the nature of the mental disturbance expressing itself by them._ _Now I have undertaken the work of investigating (as much as possible after your method), the tendencies of the fashions in art and literature; of proving that they have their source in the degeneracy of their authors, and that the enthusiasm of their admirers is for manifestations of more or less pronounced moral insanity, imbecility, and dementia._ _Thus, this book is an attempt at a really scientific criticism, which does not base its judgment of a book upon the purely accidental, capricious and variable emotions it awakens--emotions depending on the temperament and mood of the individual reader--but upon the psycho-physiological elements from which it sprang. At the same time it ventures to fill a void still existing in your powerful system._