[When Leibniz and Spinoza met in The Hague in 1676] The encounter between the two greatest philosophers of the seventeenth century in fact extended over several days. From a letter Leibniz posted to the Duke of Hanover's secretary from Holland, it is possible to infer that the courtier arrived in The Hague on or before November 18 and remained for at least three days and possibly as much as one week. Leibniz later told his Parisian friend Gallois that he had conversed with Spinoza "many times and at great length".