In his book Kant: A Biography, Manfred Kuhen has examined the intellectual connection between Immanuel Kant and Moses Mendelssohn. Here’s an excerpt from the book (Chapter 5: "Silent Years") in which Kuhen is describing Kant’s reaction to Mendelssohn’s visit to Königsberg:
In July of 1777 ones Mendelssohn, one of the most important German philosophers of the late Enlightenment, came for a visit to Königsberg. He was perhaps the dominant force on the German philosophical scene between 1755 and 1785. His work in aesthetic theory and on the nature and role of sensibility was especially influential, and it would be difficult to understand the development of German thought from Wolffian rationalism to Kantian idealism without paying close attention to Mendelssohn. If he was received like royalty by the Jewish community, he was treated with almost equal respect by the philosophical community. Kant and Hamann were especially happy to see him. After a trip to Memel, Mendelssohn stayed another ten days in Königsberg (August 10-20). Kant wrote to Herz in Berlin:
Today Mr. Mendelssohn, your worthy friend and mine (for so I flatter myself), is departing. To have a man like him in Königsberg on a permanent basis, as an intimate acquaintance, a man of such gentle temperament, good spirits, and Enlightenment - how that would give my soul the nourishment it has lacked so completely here, a nourishment I miss more and more as I grow older! I could not arrange, however, to take full advantage of this unique opportunity to enjoy so rare a man, partly from fear lest I might disturb him . . . in the business he had to attend to locally. Yesterday he did me the honor of being present at two of my lectures, d la fortune du pot, as one might say, since the table was not prepared for such a distinguished guest... I beg you to keep for me the friendship of this worthy man in the future...
One may well wonder what difference such a Mendelssohnian influence might have made to Kant's critical enterprise. Would the Critique of Pure Reason — which Kant was busily writing at that time — have looked any different? We will, of course, never know the answer to such questions.