I have a secret to-do list. The problem with this to-do list is that it’s easy for me to forget what is on it. Because it’s not anywhere extant in writing—that’s how secret it is. If it were recorded anywhere outside my mind, it wouldn’t be so secret. Even if were perfectly hidden from the eyes of others, I would still know where it was and would be tempted to look at it. So it would be a secret from all others, but not from me. If it’s not written down, I can’t look at it, and so it can be a secret from me too—just to the extent that I don’t remember I have it. But this is the trouble, that in order to preserve its secrecy, I don’t often call it to mind—or, I sometimes call to mind individual items that happen to be on the list, but not often in the context of the list, and I very rarely think of the list as a whole. And the trouble is that because of this, I run the risk of forgetting its structure—and should I forget the structure of the list, even if I remember, individually and not necessarily at the same time, each of its items,—then the list is no longer. Because it exists only in my mind, you see—there’s nothing and no one else to testify to it.