- Sigmund Freud: All feminine frailties, and perhaps most human frailties, were foreign to her or had been conquered by her in the course of her life.
- Sigmund Freud: I was transfixed by your empty chair, almost unable to lecture without your presence.
- Rainer Maria Rilke: Lou-how splendid you are! What space you have opened in me. You are not a goal to me. You are a thousand goals. You are everything.
- Friedrich Nietzsche: ...the most intelligent of all women. Sharp as an eagle and courageous as a lion, and yet an utterly feminine girl.