The man who wrote The Star of Redemption is of a different caliber from the author of Hegel and the State. Yet when all is said and done, the new book is only – a book. I don't attach any undue importance to it. The small – at times exceedingly small – thing called (by Goethe) 'demand of the day' which is made upon me in my position at Frankfort, I mean the nervewracking, picayune, and the same time very necessary struggles of people and conditions, have now become the real core of my existence – and I love this form of existence despite the inevitable annoyance that goes with it.

Cognition [Erkennen] no longer appeals to me as an end in itself….. [whereas] the questions asked by human beings have become increasingly important to me. This is precisely what I mean by 'cognition and knowledge as a service': a readiness to confront such questions, to answer them as best I can out of my limited knowledge and my even slighter ability. You will now be able to understand what keeps me away from the university …

Rosenzweig to Meinecke, cited here.