The work presents a polemical survey of late-century cultural trends, arguing that recent artistic and literary fashions—mysticism, symbolism, egoism, aestheticism, decadence, and naturalistic realism—reflect underlying mental degeneration among their creators. Using contemporary psychiatric and anthropological ideas, the author identifies characteristic symptoms, explores alleged causes, and analyzes representative movements and figures as manifestations of pathological temperament. The closing chapters offer a prognosis for society and propose moral, cultural, and therapeutic remedies intended to counteract what he sees as corrosive influences on public taste and youth.