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gwern comments on My Wild and Reckless Youth - Less Wrong
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Retrospective prediction is an expansion of http://en.wikipedia.org/wiki/retrodiction
Oh, thank you, Gwern! Ok, so retrodiction is more like this: There are facts that we currently know and phenomena that have already happened so you should consider whether your theory would have predicted them. It's not "did something related precede this" but "If we had known this theory before realizing certain facts or making certain observations, would the theory have predicted or explained these?"
Hmm for examples... if there were an all-knowing, all-powerful, all-loving God, what would I predict? If life on earth evolved, what would I predict?
What would God do? Make something awesome or lounge around feeling enlightened. I'm personifying here, and I know it... I have no idea what a God would do but I suspect that it would not be "Make a bunch of creatures knowing that a bunch of them will experience horrible suffering. Demand that they have faith but confuse them with a bunch of different religions to choose from. Create each of them knowing exactly how they'll reason and what they'll experience and what that combination will result in and demand certain beliefs that won't make sense to some of them."
Whereas with evolution, I'd predict that various life forms would evolve, some would succeed, some would not, life would be more like a chaotic experiment than a harmonious symphony, the smartest life forms would be dreadfully confused for quite some time before having it together...
And this sounds like earth.
Yes, that's pretty much what retrodiction is. It's not as good as prediction since you can come up with theories over-fitted to exactly the past (a big problem with financial retrodiction: people routinely find some complex strategy or apparent arbitrage when running over the last 30 years of market data, which disappears the moment they tried to use it), but if predictions are unavailable, at least retrodiction keeps you concretely grounded.
I'm not sure I would use God as an example. Theists like Plantinga have done a good job showing that they can come up with a version of God + concepts like 'free will' which is logically consistent with any observation, so neither retrodiction nor prediction matters for their God.
I love it. Retrodiction is awesome.
I think I broke the free will God argument. The idea that evil is evidence that God gives us free will is contradicted by the existence of evil. What do you think?
In general, if someone thinks they've said something that is both new and valuable about the theodicy: they haven't.
Looking at your link, I have no idea what you're trying to say.
Well, I reworded my point as "The idea that evil is evidence that God gives us free will is contradicted by the existence of evil" but if you don't think it's going to be interesting, don't bother.