For very many people it will be a hard nut to crack if they are told to believe that when men grow old they do not become weak or even feeble-minded, but more psychic and more spiritual. Only, when the body is worn out, we can no longer express the psycho-spiritual which we have cultivated, through the body. It is like the case of a pianist: he might become a better and better player, but if his piano is worn out we cannot perceive this. If you were only to know his capabilities as a pianist from his plane (? play, I presume), you will not be able to gather much if the piano is out of tune and has broken strings. So that Kant, when he was an old man and “feeble-minded” was not weak minded as regards the spiritual world; there he had become glorious.
Source: Rudolf Steiner – GA 181 – Anthroposophical Life Gifts – Lecture III: Thoughts about the Life Between Death and Rebirth – Berlin, 2nd April 1918
Translated by Harry Collison