Epistemic status: physical certainty
According to all known laws of physics, our universe obeys CPT symmetry. In layman's terms, "an antimatter, mirrored, and time reversed universe would behave exactly the same as our regular universe."
It stands to reason that moral laws should have the same symmetries as physical ones. This follows immediately if you're a materialist, but even if not, it would be strange indeed if two systems that behaved the same in every physical way were morally distinct. But what consequences does CPT symmetry hold for moral philosophy?
Imagine a happy person who generates one utilon per second. The goodness of their experience is directly linked to the passage of time. If we slowed down time by a factor of two, their experience would proceed at half the usual rate and generate 0.5 utilons per second. Freezing time would mean suspending all their mental processes—with no subjective experience, the person would cease to generate utilons at all.
What happens if we reverse the direction of time for this person? Instead of generating utilons, they are now absorbing them, canceling out the positive experiences of another happy person. An experience with positive value has negative value when time is reversed. This result may seem counterintuitive, but it is how other dynamical quantities like electric current and momentum behave, and is required by smoothness.
Let us assume that the value of affective states is invariant under parity transformations: flipping a person right to left should not change the valence of their experience.
Then, for utility to be invariant under the combination of C, P, and T symmetries, switching from matter to antimatter must also mean a sign flip to utility. The "suffering" of a person made out of antiparticles would actually be a good thing, as it would negate the suffering of a person made of ordinary matter.
This would explain one of the great mysteries in physics—why is there more matter than antimatter? Brian Tomasik has proposed that even elementary particles such as electrons may suffer; suppose instead that they have positive experiences. Then the anti-experiences of positrons, their antimatter counterparts, must have negative value.
Assuming the universe had a benevolent creator, it must contain more good than bad, on net. An imbalance of matter and antimatter would be necessary for this to be the case, at least on the level of particles.
In fact, for every antiparticle in the observable universe there are one billion matter particles, so we can rest easy knowing that the suffering of positrons is overwhelmed by the joy of electrons.
