 Hasker claims that this objection is confused, conflating two quite distinct questions (Hasker 1989:208–09). One is a metaphysical question: What does it mean to say of a person at one time that she is numerically the same person at a later time? (Or, if you like, it is a metaphysical question to ask: Is x at t1 the same φ as y at t2?) The second is an epistemological question: How can we tell that a person at one time is numerically the same person at a later time? (Or how can we tell that x at t1 is the same φ as y at t2?) The failure to distinguish these questions (a failure which may be due in part to Wittgenstein) is the source of serious philosophical confusions. The short answer to the first question is that normally, when we know what a φ is, we know also what it is for a φ at t1 to be the same individual φ as a φ at t2. The abnormal cases are those in which the φ at t1 has undergone changes, and we are unsure whether those changes amount to the destruction of the φ, or its replacement by another object, so that the very same φ cannot possibly have persisted until t2. The classic example is the ship of  Theseus,[1]  but there are many others. In such cases, our first recourse is to seek to understand more accurately the concept of a φ—does our concept of a ship, for example, allow for the progressive replacement of all of the ship’s parts, or not? But sometimes there may be no determinate answer to this question. Our concepts, after all, have been developed to deal with the sorts of contingencies that normally arise, and it may sometimes be possible to invent scenarios (or even to discover them empirically) that are not provided for in our ordinary usage of a concept. In that case, we must either provide for ourselves criteria to cover the novel situation (thus modifying our previous concept of a φ), or else admit that the question we were asking has no answer.