For two years Lessing remained at Berlin; busy years, in which he scattered these treatises teeming with discernment and genius. Then at the end of that time he felt himself exhausted, he craved seclusion, in which he could once more live for himself and garner up fresh stores of knowledge. The city and his numerous friends were too distracting. So one day he stole away without previous warning and installed himself in the quiet university town of Wittenberg. At Wittenberg he spent a year of quiet study. The University library was freely opened to him, and he could boast that it did not contain a book he had not held in his hands. Wittenberg: being chiefly a theological university, Lessing's attention was principally attracted to that subject, and he here laid the foundations of the accurate knowledge that was in after years to stand him in great stead. When he had exhausted all that Wittenberg could offer, he one day (1752) reappeared at Berlin as unexpectedly as he had quitted it, and quickly resumed his old relations there, which proved as busy and significant as before. Lessing again maintained himself by authorship, but this time his productions were riper. He published several volumes of his writings. They contained treatises composed at Wittenberg, Rehabilitations (_Rettungen_) of distinguished men, whom he held the world had maligned, as well as several plays, among which were the 'Jews,' 'The Woman-hater,' 'The Freethinker,' 'The Treasure,' as well as the fragmentary play 'Samuel Henzi,' a novel attempt to treat of modern historical incidents on the stage. A somewhat savage attack, entitled 'Vade mecum,' in which he criticised unsparingly a certain Pastor Lange's rendering of 'Horace,' drew upon Lessing the attention of the learned world, and since he was in the right in his strictures, they regarded him with mingled fear and admiration. His renewed criticisms in Voss's _Gazette_ further maintained his reputation as a redoubtable critic. These were happy, hopeful years in Lessing's life; he enjoyed his work, and it brought him success. He had, moreover, formed some of the warmest friendships of his life with the bookseller Nicolai and the philosopher Moses Mendelssohn. With the former he discoursed on English literature, with the latter, on æsthetic and metaphysical themes. Their frequent reunions were sources of mental refreshment and invigoration to all three. What cared Lessing that his resources were meagre, he could live, and his father was growing more reconciled now that men of established repute lauded his son's works. Together with Mendelssohn, Lessing wrote an essay on a theme propounded by the Berlin Academy, 'Pope a Metaphysician!' that did not obtain the prize, as it ridiculed the learned body which had proposed a ridiculous theme, but it attracted notice.