A fined tuned argument.....Heywood style.

[Heywood]

If A and B both have a 50% probability of being true then the probability of the existence of a creating intellect goes above 50%.

The reason this would be the case is because 50% of the time A is true and by necessity of it being true a creating intellect exists.

However if B is true the multiverse itself could still have been created by an intellect. Unless you can show the existence of a multiverse positively excludes the existence of a creating intellect, you have to acknowledge there is some probability, call it X, that a creating intellect exists. X might be exceedingly small...but it is not 0.

If A and B are equally likely, the probability of the existence of a creating intellect is 50% + X.

The principle of indifference states that if the n possibilities are indistinguishable except for their names, then each possibility should be assigned a probability equal to 1/n.

Since you're now claiming we have additional information (that B could be caused by an intellect), then the Principle of Indifference no longer applies (indeed, never applied, as we have many ways of distinguishing these alternatives). So you've just eliminated the Principle of Indifference as a valid rule for applying probabilities, so you cannot any longer say that the probabilities should be assigned 50 / 50 on that basis. You never could. You've misapplied the Principle of Indifference.

The two possibilities are indistinguishable in objective ways to determine their probability. And keep in mind we aren't talking about exact probabilities...it would be enough to simply have an objective means of showing the probability of A is greater than B or the probability of B is greater than A. We don't have that here.

Now you are claiming we do have it here because possibility A requires something extra....the existence of an intellect. Well possibility B requires something extra too...the existence of a mechanism for generating the sub universes.

I'm glad to see you did some homework but you really haven't shown I have misapplied the principle of indifference. To do that you have to somehow show that the probabilities of A and B are different from each other...that they can be distinguished in some objective way.