But that is not to say that we are in doubt because it is possible for us to imagine a doubt. I can easily imagine someone always doubting before he opened his front door whether an abyss did not yawn behind it, and making sure about it before he went through the door (and he might on some occasion prove to be right)—but that does not make me doubt in the same case
But, if you are certain, isn’t it that you are shutting your eyes in face of doubt?”—They are shut.
That sounds almost Wittgenstenian