It is always interesting to know the circumstances under which pieces that have moved a world were originally composed, and Rousseau's account of the generation of his thoughts as to the influence of enlightenment on morality, is remarkable enough to be worth transcribing. He was walking along the road from Paris to Vincennes one hot summer afternoon on a visit to Diderot, then in prison for his Letter on the Blind (1749), when he came across in a newspaper the announcement of the theme propounded by the Dijon academy. "If ever anything resembled a sudden inspiration, it was the movement which began in me as I read this. All at once I felt myself dazzled by a thousand sparkling lights; crowds of vivid ideas thronged into my mind with a force and confusion that threw me into unspeakable agitation; I felt my head whirling in a giddiness like that of intoxication. A violent palpitation oppressed me; unable to walk for difficulty of breathing, I sank under one of the trees of the avenue, and passed half an hour there in such a condition of excitement, that when I arose I saw that the front of my waistcoat was all wet with my tears, though I was wholly unconscious of shedding them. Ah, if I could ever have written the quarter of what I saw and felt under that tree, with what clearness should I have brought out all the contradictions of our social system; with what simplicity I should have demonstrated that man is good naturally, and that by institutions only is he made bad."[153] Diderot encouraged him to compete for the prize, and to give full flight to the ideas which had come to him in this singular way.[154]