This Pirandello quote is a nice way to frame the letter writing exercise:
"I’m only asking you to try and find out if you really see yourself now in the same way that you saw yourself in the past, with all the illusions you had then, with everything inside and outside yourself as it seemed then – and not only seemed, but really was! Well then look back on those allusions, those ideas that you don’t have any more, on all those things that no longer seem the same to you. Don’t you feel that not only this stage is falling away from under your feet but so is the earth itself, and that all these realities of today are going to seem tomorrow as if they had been an illusion? I only want to make you see that if we have no other reality outside our own illusion, perhaps you ought to distrust your own sense of reality, whatever you touch and believe in and that seems real for you today, is going to be – like the reality of yesterday – an illusion tomorrow."