The soul, indeed, does not change. It never descends from the stage once reached. But its instrument has become weak, like a great pianist who can no longer play as he played formerly, if he has a bad instrument. You will say the soul no longer knows its own stage. Yes, the soul does not see itself as long as it is in a physical body. There is only to be found the reflection of the soul, the mirror image. Now the mirror becomes clouded or broken. Then it can no longer reflect.
Source: Rudolf Steiner – GA 97 – The Christian Mystery – Leipzig, 16th March 1907