  The other event occurred on the occasion of a long journey that took Jacobi, on July 5, 1780, to Wolfenbüttel, where Lessing was librarian at the Herzog August’s library. Jacobi immediately paid a visit to the famous man, and it was there, while a guest at Lessing’s house, that Jacobi engaged his host in that now famous conversation in which, according to Jacobi’s report, Lessing declared himself to be a Spinozist (Jacobi, 1785: 10–45). This alleged revelation, made only a few months before Lessing’s sudden death (1781), was to be the occasion of an exchange of letters between Jacobi and Moses Mendelssohn on the nature of philosophy in general and Spinozism in particular.  Mendelssohn was well known at the time as Lessing’s great friend, and as himself an artificer of the German Enlightenment. The exchange began in 1783 (Jacobi, 1785: 1), and continued in a period of time when Jacobi was deeply in sorrow because of the premature death of his beloved Betty (1784) and of a younger son, and was also suffering from bad health. As the result of an intricate and unpleasant set of circumstances — one that was to provide fodder to opposing parties, in the dispute that soon followed, for questioning the integrity of both Mendelssohn and Jacobi — the latter published the letters in 1785, complete with commentary, under the title of Concerning the Doctrine of Spinoza in Letters to Herr Moses Mendelssohn (Spinoza Letters).