I've made this point a number of times, but apparently I'm not tired of making it, because I'm about to make it again. One of the tenets of Objectivism is that adherence to the principles of Objectivism is a necessary condition for true happiness and maximum longevity. I am completely confident that this is false. So I am also willing to bet that Mormons, for example, are on average both happier (measured according to any standard method) and longer lived than Objectivists.
Any takers? How much you wanna bet?
I anticipate that some will object that happiness measurement techniques are unreliable. Fair enough! But I worry some Objectivists will insist on defining happiness a bit circularly. Rand said happiness is “the successful state of life… that state of consciousness which proceeds from the achievement of one's values.” I like it. Elsewhere we get “noncontradictory joy,” by which she means guilt-free joy. Anyway, how can we tell we're there? By noticing that we're in that joyfully guilt-free state of consciouness. It seems like if you were in it, you'd know it. That sure sounds to me like something strong enough to show up on surveys or experience sampling diaries. Still, I think Mormons will report feeling better. The trick is that happiness, by definition, comes from achieving one's (objective) values, and objective values are the necessary conditions for life (“man qua man”). Reason, the capacity of non-contradictory identification, is our primary instrument of survival and happiness, and faith is the abdication of reason. Mormons believe, well, lots of weird things, by faith, totally at odds with reality. So whatever state of consciousness Mormons are achieving, it can't really be happiness, now can it, since it violates allegedly practically mandatory values.
But you'd think the “philosophy for living on Earth” would buy you some extra longevity, so it's hard to see how you would explain away Mormon dominance in life-span, if such a thing were shown to be true. (And I'll bet you it is!) Since one man's modus ponens is another's modus tollens, we might infer from the fact that adherence to some belief system leads to the longest, happiest lives, together with the premise that reason is our capacity of non-contradictory identification aimed at survival and flourishing, to the conclusion that the most life-promoting belief system must be endorsed by reason. So if Mormons really are happier and longer-lived, should Objectivists become Mormons? Or should they rather acknowledge that reason isn't necessarily for survival and happiness, but worth caring about all the same, and believing in Kolob or whatever isn't worth it, even it would make you happier and add a couple years.