The thought reproduced in the above epigraph is taken from an article by Thurau et al. [1], who attribute it to Arthur Schopenhauer (17881860), an outstanding philosopher and author of the far-reaching piece Die Welt als Wille und Vorstellung (The World as Will and Representation). In German, it would perhaps read as etwas denken, das niemand vorher gedacht hat, während etwas sehen, was jeder sieht. We could not assert whether Schopenhauer really said that, but it should not be at all surprising if it were, because it sounds simple, perhaps even naïve, and very deep, indeed. It fits perfectly to Carl Friedrich Wilhelm Ludwigs personality (18161895), whom we will look at as physiologist in this second note. Yes, second note-because in the first one [2], we looked at him as bioengineer. A third and last Retrospectroscope column completing this series will deal with his wonderful and always humble and generous activities as teacher.