The case for atheistic reductionism is not a slam-dunk.
While atheistic reductionism is clearly simpler than any of the competing hypotheses, each added bit of complexity doubles the size of hypothesis space. Some of these additional hypotheses will be ruled out due to impossibility or inconsistency with observation, but that still leaves a huge number of possible hypotheses that each add take up a tiny amount of probability mass, but they add up.
I would give atheistic reductionism a ~30% probability of being true. (I would still assign specific human religions or a specific simulation scenario approximately zero probability.)
Assuming our MMS-prior uses a binary machine, the probability of any single hypothesis of complexity C=X is equal to the total probabilities of all hypotheses of complexity C>X.
I was very interested in the discussions and opinions that grew out of the last time this was played, but find digging through 800+ comments for a new game to start on the same thread annoying. I also don't want this game ruined by a potential sock puppet (whom ever it may be). So here's a non-sockpuppetiered Irrationality Game, if there's still interest. If there isn't, downvote to oblivion!
The original rules:
Enjoy!