Encouraged by this, I wrote in Hebrew a dissertation in which I brought into doubt the foundations of Revealed as well as of Natural Theology. All the thirteen articles of faith, laid down by Maimonides, I attacked with philosophical arguments, with the exception of one, namely the article on reward and punishment, which I conceded merely in its philosophical interpretation, as referring to the natural consequences of voluntary actions. I sent this dissertation to Mendelssohn, who was not a little amazed, that a Polish Jew, who had scarcely got the length of seeing the Metaphysics of Wolff, was already able to penetrate into their depths so far, that he was in a position to shake their results by means of a correct Ontology. He invited me to visit him, and I accepted his invitation. But I was so shy, the manners and customs of the Berliners were so new to me, it was not without fear and embarrassment, that I ventured to enter a fashionable house. When therefore I opened Mendelssohn's door, and saw him and other gentlefolks who were there, as well as the beautiful rooms and elegant furniture, I shrank back, closed the door again, and had a mind not to go in. Mendelssohn however had observed me. He came out and spoke to me very kindly, led me into his room, placed himself beside me at the window, and paid me many compliments about my writing. He assured me, that, if I went on in this way, I should in a short time make great progress in Metaphysics; and he promised also to resolve my doubts. Not satisfied with this, the worthy man looked after my maintenance also, recommended me to the most eminent, enlightened and wealthy Jews, who made provision for my board and other wants. Their tables I was at liberty to enjoy when I chose, and their libraries were open to my use.
Especially worthy of mention among these gentlemen was H——, a man of many attainments and excellent disposition, who was a particular friend and disciple of Mendelssohn. He took great pleasure in my conversation, often discussed with me the most important subjects in Natural Theology and Morals, on which I expressed my thoughts to him quite frankly and without disguise. I went over with him in a conversational way all the systems known to me that are generally denounced, and defended them with the greatest pertinacity. He met me with objections; I answered them, and brought in my turn objections against the opposite systems. At first this friend regarded me as a speaking animal, and entertained himself with me, as one is apt to do with a dog or a starling that has been taught to speak a few words. The odd mixture of the animal in my manners, my expressions, and my whole outward behaviour, with the rational in my thoughts, excited his imagination more than the subject of our conversation roused his understanding. By degrees the fun was turned to earnest. He began to give his attention to the subjects themselves; and as, notwithstanding his other capabilities and attainments, he had no philosophical head, and the liveliness of his imagination generally interfered with the ripeness of his judgment, the results of our conversations may be readily imagined.
A few examples will be sufficient to give an idea of the manner in which I conducted a discussion at the time, of the ellipses in my diction arising from my deficiency in expressions, and of the way in which I illustrated everything by examples. I endeavoured once to make Spinoza's system intelligible,—to show that all things are merely accidents of a single substance. My friend interrupted me and said, "But, good heavens! are not you and I different men, and do we not each possess an existence of our own?" "Close the shutters," I called in reply to his objection. This strange expression threw him into astonishment; he did not know what I meant. At last I explained myself. "See," said I, "the sun shines through the windows. This square window gives you a square reflection, and the round window a round reflection. Are they on that account different things, and not rather one and the same sunshine?"
On another occasion I defended Helvetius' system of self-love. He brought against it the objection, that we surely love other persons as well as ourselves. "For instance," said he, "I love my wife;" and to confirm this he gave her a kiss. "That proves nothing against me," I replied. "For, why do you kiss your wife? Because you find pleasure in doing it."
Herr A—— M—— also, a good honest fellow, and at that time a wealthy man, allowed me free access to his house. Here I found Locke in the German translation, and I was pleased with him at the first hasty glance, for I recognised him as the best of the modern philosophers, as a man who had no interest but the truth. Accordingly I proposed to the tutor of Herr A—— M——, that he should take lessons from me on this admirable work. At first he smiled at my simplicity in proposing, that I, who had scarcely got the length of seeing Locke, should give lessons to him whose native tongue was German, and who had been brought up in the sciences. He acted, however, as if he found nothing offensive in the matter, accepted my proposal, and fixed an hour for the lessons. I presented myself at the time appointed, and began the lessons; but as I could not read a word of German correctly, I told my pupil to read aloud paragraph by paragraph in the text, and that then I should give him an exposition of each. My pupil, who pretended to be in earnest, consented to this also, to carry on the joke; but how great was his astonishment when he found, that no joke was to be played in the matter, that in fact my expositions and remarks, though delivered in my own peculiar language, evinced a genuine philosophical spirit.
It was still more amusing, when I became acquainted with the family of Widow Levi, and made the proposal to her son, the young Herr Samuel Levi,[53] who is still my Maecenas, that he should take lessons from me in the German language. The studious youth, incited by my reputation, was resolved to make a trial, and wished me to explain Adelung's German Grammar. I, who had never seen Adelung's Grammar, did not allow myself to be at all disconcerted on this account.[54] My pupil was obliged to read Adelung bit by bit, while I not only expounded it, but added glosses of my own. In particular I found a good deal to take exception to in Adelung's philosophical explanation of the parts of speech; and I drew up an explanation of my own, which I communicated to my intelligent pupil, by whom it is still preserved.
As a man altogether without experience I carried my frankness at times a little too far, and brought upon myself many vexations in consequence. I was reading Spinoza. His profound thought and his love of truth pleased me uncommonly; and as his system had already been suggested to me by the Cabbalistic writings, I began to reflect upon it anew, and became so convinced of its truth, that all the efforts of Mendelssohn to change my opinion were unavailing. I answered all the objections brought against it by the Wolfians, brought objections against their system myself, and showed, that, if the nominal definitions of the Wolfian Ontology are converted into real definitions, conclusions the very opposite of theirs are the result. Moreover, I could not explain the persistency of Mendelssohn and the Wolfians generally in adhering to their system, except as a political dodge and a piece of hypocrisy, by which they studiously endeavoured to descend to the mode of thinking common in the popular mind; and this conviction I expressed openly and without reserve. My friends and well-wishers, who for the most part had never themselves speculated on philosophical subjects, but blindly adopted the results of the systems prevailing at the time as if they were established truths, did not understand me, and therefore also were unable to follow me in my opinions.
Mendelssohn, whose usual course was to tack, did not wish to oppose my love of inquiry, secretly even took pleasure in it, and said, that at present indeed I was not on the right road, but that the course of my thoughts must not be checked, because, as Descartes rightly remarked, doubt is the beginning of thorough philosophical speculation.