This book explains how illustrated philosophy, modern sociology and critical thinking have confronted the dark and irrational world. Melancholy is the symbol of chaotic darkness, and so as its pathway of sadness: boredom, insanity, anguish, depression, mourning, weariness, sublime fear and the existential nausea. The illustrated-modern thinking does not usually see the dark and frequently denies it. Roger Bartra raises a weird enigma: why do irrationality and mental disorder manage to stay in the heart of modern culture, influenced by rationalism? He reaches Kant, Weber and Benjamin for the answer. These thinkers were not visionary enough to orient themselves through the dark path of irrationality; however, their blindness, trips and falls allow us to find the light in the dullness, hidden to their gaze. Bartra makes a fascinating experiment: he takes the three distinguished blind, which are incapable of seeing the dark face of the melancholy angel, and uses them as guides. Used to the bright light of their ideas, the three of them recognized the disturbing presence of the black sun that Nerval mentions, but couldn't picture it.