From Ich warne Neugierige. Erinnerungen eines kritischen Zeitbetrachters / Walter Abendroth, pp.94-5. (My translation).
In Friedenau, there still lived my old Jewish schoolmate, Kurt Auerbach. The pride of his family was an uncle who fell out of the routine of the family's commercial activities because he had risen in the ranks of philosophy; although he was not highly regarded by academic thinkers, but in a circle of prominent persons. If my memory does not deceive me, although he was of the house of Auerbach, he named himself Constantin Brunner. My friend was of the opinion that I was of a similar cast of mind and could increase Brunner's followership. I was in fact invited to a meeting in Potsdam. The jovial gentleman with the wise, lively face and the medium-length grey-streaked hair received me wearing a brown Sammetjackett. He was extremely amiable and unorthodox. He appeared to me to be a person of great warmth and noble will, and within whom an almost childlike directness of thought was quite apparent. His manner was not without a slight arrogance, and his language was correspondingly solemn—something in the vein of the notorious Possart style. It was only once he came out with his theory that the two greatest persons who ever lived were Jesus of Nazareth and Spinoza that I realized that the continuation of this relationship would only entail mutual disappointment within the entourage. I certainly lost a not profitless source of support with the decision to leave it at that. I carefully read the dedication copy of Die Lehre von den Geistigen und vom Volke given to me on the way home. I found therein the theoretical substructure of that aristocratic intellectualism that also intermittently surrounded the sympathetic human personality of Constantin Brunner with an aura of isolating priestliness. His disciple-building was established on a religio-philosophical affirmation and ethically deepened interpretations of Old Testament leadership thought.