His last writings are the Reveries of the Solitary Walker. Each reverie is identified as a promenade, so that, he tells us, they are “a faithful record of my solitary walks and of the reveries which fill them.” (CW8.9, OC1.1002) They are the walks of a man “alone on earth” (CW8.3, OC1.995), in which, as he says, “I will apply the barometer to my soul.” (CW8.7, OC1.1000–1) The last – the tenth – is unfinished, a walk from which he does not return. In the five volumes of his collected works, it occupies two pages. And yet I exaggerate only slightly in saying that my aim in this book – in this journey that I invite you to take with Jean-Jacques Rousseau – is to understand that final promenade, why it says what it says, why it does not say what it does not say. To reach that walk will be my end, as it was his end. It is fitting that we should begin by joining Rousseau on another walk.

He is in Paris, a man of thirty-seven with literary and musical aspirations as yet unfulfilled, an associate of the intellectuals whom we have come to know as the philosophes. He is a collaborator with Denis Diderot, who had embarked on the great project of his life, the Encyclopedia that was to synthesize the knowledge and outlook of the Enlightenment.