Schopenhauer's magnum opus, the original one-volume edition of The World as Will and Representation, had fallen stillborn from the press in 1819, without attracting any attention. On the last day of that year he applied to the philosophical faculty at Berlin and asked to be included in the next catalogue (Vorlesungsverzeichnis), with a course of six lecture hours weekly on "the whole of philosophy"--and that before he had fulfilled the usual requirements for habilitation. He left it to the faculty to fix the time, but added: "the most suitable time is presumably whenever Herr Prof. Hegel gives his biggest course [sein Hauptcollegium]."
The dean, while specifically commenting on Schopenhauer's "no mean presumption and extraordinary vanity" favoured approval of the request, provided the requirements were fulfilled before he actually began to lecture. Hegel went along with this; other professors did not. One protested against inclusion of the announcement in the catalogue before the requirements were fulfilled, while another wrote: "I confess that the exceptionally great arrogance of Herr S. does not incline me very much to declare myself in favour of any special exceptions on his behalf by action of the faculty"--and several others subscribed to that.
Nevertheless, the government representative looked favourably on Schopenhauer's request, the dean so informed Schopenhauer, and the young man came to Berlin to confer with Hegel on the title of his test lecture (Probevorlesung). March 18, 1820, he wrote the dean that he had asked Hegel the day before for permission to lecture on a subject he himself had chosen, namely on four kinds of causes. "Herr Prof. Hegel very graciously granted his approval with the greatest readiness...."
It is indeed "unmistakable that Hegel placed no obstacles of any kind Schopenhauer's way." as Hoffmeister puts it. He also says: "In the whole decade from 1820 to 1831 we do not find anything more miserable regarding the lecturing by Privatdozenten of philosophy than the total of Schopenhauer." He never completed a course. After his initial approach, he was absent from Berlin for many years, then in the spring of 1826 asked permission to lecture again. He again chose the time when Hegel lectured, but not a single student showed up to hear him. The next semester he did not lecture because only one student came; after that, because only three appeared; after that, because only two came. The next three times--the topic always being the same "Foundations of Philosophy, comprehending Dianology and Logic"--nobody came; in the summer of 1830, three students; the following winter again nobody; and then Schopenhauer left again. Later he published a famous diatribe against "University Philosophy," and again and again poured out venom against Hegel in bitter polemics.
-Hegel: A Reinterpretation, Walter Kaufmann