Why the heck would the probability of seeing the evidence, conditional on the mix of all hypotheses being considered, exactly equal the prior probability of the null hypothesis?
It wouldn’t. Probably a better way to explain it would have been to factor their ratio out as a constant.
Anyway, I’ve totally messed up explaining this, so I will fold for now and direct you to a completely different argument made elsewhere in the comments which is more worthy of being considered.
Why the heck would the probability of seeing the evidence, conditional on the mix of all hypotheses being considered, exactly equal the prior probability of the null hypothesis?
It wouldn’t. Probably a better way to explain it would have been to factor their ratio out as a constant.
Anyway, I’ve totally messed up explaining this, so I will fold for now and direct you to a completely different argument made elsewhere in the comments which is more worthy of being considered.