The more I think about it, the more I am inclined to adopt the following operational principle:
THE PARTY-POOPER PRINCIPLE: Given two, roughly-equal theories, the one that is less attractive is more likely to be true.
Theories can be attractive in a variety of ways. Some theories meet deep-seated wishes, like the wish for immortality, or for free will, or to see human beings as especially noble and special sorts of beings. Some theories are just groovy, like the panpsychist view that our consciousness exists because every material thing in the universe has special flavorings inherent in it, or the view that the pyramids were made by super-intelligent aliens. Some theories give us hope, like the theory that God (or Mother Earth) won’t let global warming take us down as a species.
The problem with being attractive is that attractiveness introduces irrelevant motivations for our belief. We like to believe what puts us in a good light, or makes us feel groovy, or hopeful. That attraction is likely to skew our critical faculties, consciously or unconsciously, and get us to adopt a belief when a more clinical, detached perspective would tell us otherwise. Thus, we need to compensate for attractiveness. Thus, we need to be party-poopers.
Yes, the P-PP is pessimistic, and it is certainly possible that the flattering, groovy, hopeful theory turns out to be true. But, because of our attraction to attractive theories, we need to cultivate some bias against them, and insist that they prove themselves according to more stringent standards. In a way, the insistence levels the argumentative playing field, since the attraction tilts the field in their favor.
So, the Pragmatic Party-Pooper Corollary: If you really want to believe it, don’t.