His friends there exerted themselves to obtain for him the office of keeper of the royal library, but Frederick had not forgotten Lessing's quarrel with Voltaire, and declined to consider his claims. During the two years which Lessing now spent in the Prussian capital, he was restless and unhappy, yet it was during this period that he published two of his greatest works, Laokoon, oder fiber die Grenzen der Malerei and Poesie (1766) and Minna von Barnhelm (1767).
To him, therefore, Lessing addressed in 1778 his most elaborate answers - Eine Parabel, Axiomata, eleven letters with the title Anti-Goeze, and two pamphlets in reply to an inquiry by Goeze as to what Lessing meant by Christianity.
Kabale and Liebe, especially, is an admirable example of that "tragedy of common life" which Lessing had introduced into Germany from England and which bulked so largely in the German literature of the later 18th century.
A conversation which he had held with Lessing in 1780, in which Lessing avowed that he knew no philosophy, in the true sense of that word, save Spinozism, led him to a protracted study of Spinoza's works.
In 1760, feeling the need of some change of scene and work, Lessing went to Breslau, where he obtained the post of secretary to General Tauentzien, to whom Kleist had introduced him in Leipzig.
Instead of settling in Italy, as he intended, Lessing accepted in 1770 the office of librarian at Wolfenbiittel, a post which was offered to him by the hereditary prince of Brunswick.
Lessing also maintains that history reveals a definite law of progress, and that occasional retrogression may be necessary for the advance of the world towards its ultimate goal.
Lessing, who as a youth of twenty came to Berlin in 1 749, composed enthusiastic odes in his honour, and Gleim, the Halberstadt poet, wrote of him as of a kind of demi-god.
Under the impulse given by Lessing and Kant he turned to the original records of Christianity, and attempted to construe for himself the real significance of Christ.
From Leibnitz, Lessing, Fichte, Jacobi and the Romantic school he had imbibed a profound and mystical view of the inner depths of the human personality.