# - Mendelssohn, Moses.

a working manuscript with many important autograph revisions and additional passages written by Mendelssohn in the margins, lacking the conclusion, refuting Bonnet's thesis that human perception is based on the direct movement of the senses by an perceived object, with the autograph title "Essai de [deleted: "Cosmologie"] Psychologie, ou considerations sur les operations de l'ame, sur l'habitude et sur l'education etc...", with some excerpts from Bonnet, translated in the hands of a scribe (and a deleted passage in the hand of another), with the author's caustic comments ("...Eine vortrefliche Erklährung wie die Empfindungen mit den Bewegungen verknüpfet sind!. Sind wir nun nicht viel klüger als vorhin?..."); Mendelssohn describes Bonnet's work as being amongst the worst books ever written, the author attempting to be both witty and sound, but unfortunately managing neither



8 pages, folio (c.34 x 21cms), on two nested bifolia, 1754-1755; before 17 February 1755, apparently lacking the final 5 or 6 pages which are unknown, some browning and staining, a few small perforations on the final leaf, partly from oxidization of the ink

Moses Mendelssohn. Gesammelte Schriften. Jubiläumsausgabe, II (1931), pp.35-42

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...Vielleicht werden sich einige wundern, daß wir diese Schrift...unter die schlechten Bücher zehlen ...Dieser Schriftsteller hat in einen Mittelweg zwischen Witz und Gründlichkeit einschlag[en] woll[en], und er hat das Ungluk gehabt weder witzig noch gründlich zu schreiben.  Er strotzt von Metaphern und entlehnten Ausdrükung[en], die eben so wenig schön als richtig sind.  Sein Witz ist schal und pedantisch, seine Begriffe nur halb entwikelt, und die Beweise, die er manchemal zur Unzeit häuft, verstümmelt und ihres Nachdrukes völlig beraubt...

Mendelssohn derides as simplistic Bonnet's thesis that our senses are the sources of our understanding and that therefore our perception of objects is due to a physical movement on our senses exerted by an object.  He points out, amongst other things, that we have two eyes and yet we do not see double and our hearing is similarly sophisticated in operation.

...[in the margin:] Erstlich ist es falsch daß auf die Würkung eines Gegenstandes in die Gliedmaßen der Sinne, eine Wahrnehmung diese Gegenstandes selbst, und nicht von der Art und Weise seiner Wirkung, erfolgen sollte.  Wir sind uns niemahls des Gegenstandes selbst bewußt, und wir empfinden nicht anders von ihm als die Art, wie er auf die Sinne wirkt. Zweitens [in the text, deleted: "Erstlich"] kan ihm die Unachtsamkeit nicht vergeben werden, daß er die Bewegung als Zeichen annimmt die Gott gebraucht, um in der Seele [in the margin: "gewiße"] Vorstellungen hervorzubringen, ohne sich in der ganzen Schrift irgend zu dem System de veranlaßenden Ursachen bekennt zu haben...

This is the only source for this remarkable review. which is published in this incomplete state in the Complete Edition. In a letter to Lessing of 17 February 1755, Moses Mendelssohn described his manuscript as being written on three and a half sheets ("Bogen"), of which we have here the first two.  Mendelssohn has written the text with the assistance of two scribes, who take over from the author halfway through the second page.  Mendelssohn then writes the fifth, sixth and seventh pages himself and also revises much of the material, adding whole paragraphs and other annotations in the margins.  He also deletes the single passage written by the second scribe (on the fourth and fifth pages), one section of which did not make its way into the complete edition. 

Charles Bonnet's Essai was published in London in 1754.