It would be irrational for us to assign a very high prior probability to the thesis that spiky teal fruit is a healthy food.
If a species evolved to naturally assign a very high prior probability to the thesis that spiky teal fruit is a healthy food, it would not be irrational for them to do this.
So, what prior probabilities are rational is species relative.
Why couldn’t a species evolve to make irrational judgments? Something about McDowell’s exculpations where we wanted justifications . . .
ReplyDeleteI think our decisions about what we think is good to eat are more instinctive and habitual than rational or irrational.
ReplyDeleteThe assertion made, that a species that instinctively will eat a particular food based on its appearance is rational to do so, assumes that the food is of the same kind, and is in the same general environment, as the one that species has survived by eating. This in turn requires that the species is encountering the food in an environment similar to the one that its ancestors thrived within.
Rat poison and mousetraps change the food or its environment while they maintain the food's attractiveness. Such things don't rely on irrational behavior, just habitual or instinctive ones that are wrong for the mouse, because the setting is different.
Ian:
ReplyDeleteI agree about the relativity of "healthy", but I don't think it affects the argument. It would be irrational for us to have a high prior in spiky teal fruit being healthy _for the aliens_, or a high prior in spiky teal fruit being unhealthy _for us_. That's the kind of proposition that _for us_ should be _a posteriori_.
You're right that the issue is more often handled in a species by preferences rather than priors. That's an interesting fact.