The C, P and T symmetries of classical electromagnetism are quite clear: C negates the charge, P negates one or all three directions in space, and T reverses the direction of time. It is also clear that none of these symmetries can be realised in practice: C converts electrons, of which there are zillions everywhere, into positrons, which scarcely ever exist in the real world; P converts the real world into the looking-glass world, which as Lewis Carroll reminds us, is a figment of our imagination; and T causes time to go backwards, which, as we know, does not happen.

On the other hand, the combinations of any two of C, P and T are symmetries of classical physics, including electromagnetism: CP means that if you reverse a current, you reverse the poles of the electromagnet that the current creates. CT and PT both mean essentially the same thing, from a slightly different philosophical point of view, but with the same mathematical result. Therefore the combination of all three, CPT, is *not* a symmetry of classical physics. Please take careful note of this, I will test you on it later: CPT is NOT a symmetry of classical physics.

Now let us turn our attention to quantum mechanics. In quantum mechanics, there is a theorem called the CPT theorem, which says that CPT *is* a symmetry of quantum mechanics. Ergo, quantum physics is inconsistent with classical physics. Ergo, it is not possible to derive classical physics as a limiting case of quantum physics. Ergo, the measurement problem has no solution. Ergo, the search for a theory of everything is a pointless waste of time. Ergo, why are we wasting so much money on this problem?

I prefer to argue from a realist position, not from a mathematicist position, and take as an axiom the obvious fact that quantum mechanics *is* consistent with classical physics. If this axiom is false, then the universe could not exist. The universe does exist, ergo this axiom is correct. Ergo, the CPT theorem is false. Ergo, at least one of its assumptions is false. Now let us ask, which one of the CPT theorem’s hidden assumptions is false?

Well, I don’t want to get too technical, but the proof of the CPT theorem involves an “analytic continuation” from a Lorentzian spacetime (required for classical electromagnetism) to a Euclidean spacetime (required for quantum theory). It therefore requires spacetime to be a *complex* 4-space, not a real 4-space. But spacetime, in actual hard physical reality, is real, not complex. This is a clear, and obviously false, hidden assumption.

So, if any physicist cares to argue this with me, I will prove that if the CPT theorem holds, then the universe does not exist. Or, in contrapositive form, I will prove that if the universe exists, then the CPT theorem is false. It then depends whether the physicist is a theorist or an experimentalist: if the former, they will dogmatically assert that the CPT theorem is a correct statement about the universe, and will therefore be forced to deny their own existence and that of the entire universe; if the latter, they will (dogmatically?!) assert that they and the universe do exist, and will then set about designing an experiment to test the CPT theorem to destruction.