>it is very irrational to write sealed letters to a dead person.
It seems irrational when you presume that the only purpose of a letter is to be read by the recipient. But writing a letter can help clarify your own thoughts and feelings, which is a perfectly rational thing to want to do.
Have you really never written something down just to clarify your thoughts? It's legitimately useful. Usually I don't do it by writing a letter to someone, but I could definitely see doing that in Feynman's situation.
It seems irrational when you presume that the only purpose of a letter is to be read by the recipient. But writing a letter can help clarify your own thoughts and feelings, which is a perfectly rational thing to want to do.