The now largely forgotten J.C. Friedrich Schulz was a prolific and popular writer of the late Enlightenment in Germany. In December 1790, he published thirty aphorisms — or “Zerstreuete Gedanken” — in the Deutsche Monatsschrift. One of them struck me as familiar:
Hardly any teachers of a faith defend their dogmas because they are convinced of their truth, but rather because they have maintained their truth......[Die wenigsten Glaubenslehrer vertheidigen ihre Dogmen, weil sie von ihrer Wahrheit überzeugt sind, sondern, weil sie ihre Wahrheit behauptet haben.] 
This is remarkably similar to an aphorism that appeared in G.C. Lichtenberg’s private notebooks between 1789 and 1793:
Most teachers of a faith defend their propositions, not because they are convinced of their truth, but rather because they have once maintained their truth......[Die meisten Glaubens-Lehrer verteidigen ihre Sätze, nicht weil sie von der Wahrheit derselben überzeugt sind, sondern weil sie die Wahrheit derselben einmal behauptet haben.] 
As well as philosophical sketches and aphorisms, Lichtenberg’s Sudelbücher contain observational fragments, literary references, and quotations that struck him as worthy of note. So far as I know, it has not been previously observed that this particular aphorism is a close paraphrase of Schulz’s published one.
 F. Schulz, “Zerstreuete Gedanken”, nr.12, Deutsche Monatsschrift, 3.Bd., Dezember 1790, p.382, digitalised by Universitätsbibliothek Bielefeld. (A further thirty aphorisms were published in Ibid., 1.Bd, Februar 1791.)
 G.C. Lichtenberg, Sudelbücher, (Frankfurt am Main und Leipzig: Insel Verlag, 1984), J.502 from Sudelbuch J (1789-1793), p. 387.