Followup to: Probability is in the Mind

"Reality is that which, when you stop believing in it, doesn't go away."
—Philip K. Dick

There are two kinds of Bayesians, allegedly. Subjective Bayesians believe that "probabilities" are degrees of uncertainty existing in our minds; if you are uncertain about a phenomenon, that is a fact about your state of mind, not a property of the phenomenon itself; probability theory constrains the logical coherence of uncertain beliefs. Then there are objective Bayesians, who... I'm not quite sure what it means to be an "objective Bayesian"; there are multiple definitions out there. As best I can tell, an "objective Bayesian" is anyone who uses Bayesian methods and isn't a subjective Bayesian.

If I recall correctly, E. T. Jaynes, master of the art, once described himself as a subjective-objective Bayesian. Jaynes certainly believed very firmly that probability was in the mind; Jaynes was the one who coined the term Mind Projection Fallacy. But Jaynes also didn't think that this implied a license to make up whatever priors you liked. There was only one correct prior distribution to use, given your state of partial information at the start of the problem.

How can something be in the mind, yet still be objective?

It appears to me that a good deal of philosophical maturity consists in being able to keep separate track of nearby concepts, without mixing them up.

For example, to understand evolutionary psychology, you have to keep separate track of the psychological purpose of an act, and the evolutionary pseudo-purposes of the adaptations that execute as the psychology; this is a common failure of newcomers to evolutionary psychology, who read, misunderstand, and thereafter say, "You think you love your children, but you're just trying to maximize your fitness!"

What is it, exactly, that the terms "subjective" and "objective", mean? Let's say that I hand you a sock. Is it a subjective or an objective sock? You believe that 2 + 3 = 5. Is your belief subjective or objective? What about two plus three actually equaling five—is that subjective or objective? What about a specific act of adding two apples and three apples and getting five apples?

I don't intend to confuse you in shrouds of words; but I do mean to point out ...

The_Compassionate_Cynic

The_Compassionate_Cynic

The_Compassionate_Cynic

The_Compassionate_Cynic