There was something fishy, Wittgenstein thought, about a certainty which is at once empirical and immune to doubt. Yet that is just what Moore's truisms seemed to be: though certain, they seem to have no ground at all. Could that signify that they did not need one? What one could say is they were beyond the reach of any practical doubt. In On Certainty, Wittgenstein wrestled with the question how there can be such certainties, a task which a Kantian might call transcendental. Contingent propositions are characteristically doubtable, confirmable and capable of dispute. Even though no one has occasion to question them, we can imagine that someone might. And even if no one asks for proof we can imagine what a proof would be. But Moore's truisms do not appear open either to question or proof. Are they a priori, grammatical, then? No, for questions and doubts about them make some kind of sense. Then they are contingent. No, since we do not have evidence or empirical proof of them. Then what kind of proposition are they? The truisms are characterized by the questions we do not ask and doubts we do not have. But that is a statement about us. Someone from another culture might raise questions that we do not, amazed that we take such things for granted. But to imagine someone asking such questions we have to imagine a perspective very different from ours a very different Weltbild or picture of the world. Otherwise the questions fall beyond our comprehension. We cannot raise a question whether the world is very old, for if we did, that would bring into question the whole structure of geology, which is precisely the method by which we date things. If, for instance, we try to step back from that system and raise our question, we operate in a procedural and conceptual vacuum. Geology seems to rest upon or incorporate that proposition. Yet a question about whether the world is old has the same form and even the same kind of matter as the question whether this rock is very old. How can there be a problem for the one but not for the other? We face what appears tp be a logical discontinuity as we go from the one question to the other. Some kind of boundary has been crossed. But if it is not the boundary between contingent and necessary propositions, what boundary is it?