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Comment by fragsworth | Hacker News Reader

On "Intuition 2":

> At time t, if it is true that the probability of the marble being under a given box is 0.5, then if I guessed randomly, I would be correct one out of two times on average.

> The fact that the probability is 0.5 is completely independent of whether or not any particular mind believes that it is 0.5. But this is the definition of an objective truth. Therefore, probability must be objective.

This is begging the question. The two things combined is like saying "At time t, if it is true that probability is objective... therefore probability must be objective."

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Saying p=0.5 necessarily implies the 1/2 thing. Neither implies any stance on whether it's subjective/objective so far. The 'objective' conclusion there requires the further fact of mind-independence, which is based on 'you can't change the odds that a fair coin comes up heads just by thinking about it' type arguments. So it's not circular/question-begging, IMO.

When a fair coin is tossed it will either come up heads or it wont. Put another way, the probability of getting heads is 1 or 0, unless you believe that something magical happens to the coin while it is in mid-air that somehow makes it impossible to predict what will happen when it lands (given a complete set of data).

So the outcome of the coin-toss is knowable, it just happens to be complex enough that it is not known (to us). To bridge the gap between the knowable and the not known we introduce a margin of error in our calculations, called Probability. Probability then, only exists as man-made mathematical spackle - and is by definition subjective.

To prove me wrong find an event that has an outcome that cannot be known in advance. That's why this question is on a philosophy exam.

Quantum mechanics?

Heisenberg uncertainty principle and the entire field of quantum mechanics?

Well played and conceded. So do we need two sets of rules? One for 'our world' and one for the subatomic world?

Good question. My best guess is that the law of large numbers averages out the weirdness so that you never spontaneously tunnel through the floor or whatever, but that's only a guess. And there's a lot of weirdness to deal with.

Just because relativity showed Newtonian physics to be wrong about how the universe worked doesn't mean we can't use the latter as a decent approximation under appropriate constraints. Similarly, we don't really need to calculate the probability of the Sun teleporting over Wall Street when valuing Facebook's IPO.

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