The mediation by the serpent was necessary: Evil can seduce man, but cannot become man.[Es bedurfte der Vermittlung der Schlange: das Böse kann den Menschen verfuhren, aber nicht Mensch werden.]
Source:Dearest Father: Stories and Other Writings (Schocken Books, ed. 1954), Chapter 2. Reflections on Sin, Suffering, Hope, and the True Way, Aphorisms 51, Page 39