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Randaly comments on Rationality Quotes August 2013 - Less Wrong
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That doesn't show that they're absolutely certain; it just shows that the expected value of the payoff outweighs the chance of them dying.
The real issue with this claim is that people don't actually model everything using probabilities, nor do they actually use Bayesian belief updating. However, the closest analogue would be people who will not change their beliefs in literally any circumstances, which is clearly false. (Definitely false if you're considering, e.g. surgery or cosmic rays; almost certainly false if you only include hypotheticals like cult leaders disbanding the cult or personally attacking the individual.)
Nope. "I'm certain that X is true now" is different from "I am certain that X is true and will be true forever and ever".
I am absolutely certain today is Friday. Ask me tomorrow whether my belief has changed.
In fact, unless you're insane, you probably already believe that tomorrow will not be Friday!
(That belief is underspecified- "today" is a notion that varies independently, it doesn't point to a specific date. Today you believe that August 16th, 2013 is a Friday; tomorrow, you will presumably continue to believe that August 16th, 2013 was a Friday.)
Not exactly that but yes, there is the reference issue which makes this example less than totally convincing.
The main point still stands, though -- certainty of a belief and its time-invariance are different things.
I very much doubt that you are absolutely certain. There are a number of outlandish but not impossible worlds in which you could believe that it is Friday, yet it might not be Friday; something akin to the world of The Truman Show comes to mind.
Unless you believe that all such alternatives are impossible, in which case you may be absolutely certain, but incorrectly so.
Define "absolute certainty".
In the brain-in-the-vat scenario which is not impossible I cannot be certain of anything at all. So what?
So you're not absolutely certain. The probability you assign to "Today is Friday" is, oh, nine nines, not 1.
Nope. I assign it the probability of 1.
On the other hand, you think I'm mistaken about that.
On the third tentacle I think you are mistaken because, among other things, my mind does not assign probabilities like 0.999999999 -- it's not capable of such granularity. My wetware rounds such numbers and so assigns the probability of 1 to the statement that today is Friday.
So if you went in to work and nobody was there, and your computer says it's Saturday, and your watch says Saturday, and the next thirty people you ask say it's Saturday... you would still believe it's Friday?
If you think it's Saturday after any amount of evidence, after assigning probability 1 to the statement "Today is Friday," then you can't be doing anything vaguely rational - no amount of Bayesian updating will allow you to update away from probability 1.
If you ever assign something probability 1, you can never be rationally convinced of its falsehood.
That's not true. There are ways to change your mind other than through Bayesian updating.
Sure. But by definition they are irrational kludges made by human brains.
Bayesian updating is a theorem of probability: it is literally the formal definition of "rationally changing your mind." If you're changing your mind through something that isn't Bayesian, you will get the right answer iff your method gives the same result as the Bayesian one; otherwise you're just wrong.
The original point was that human brains are not all Bayesian agents. (Specifically, that they could be completely certain of something)
Yes.
No, unless you define "rationally changing your mind" this way in which case it's just a circle.
Nope.
The ultimate criterion of whether the answer is the right one is real life.
While I'm not certain, I'm fairly confident that most people's minds don't assign probabilities at all. At least when this thread began, it was about trying to infer implicit probabilities based on how people update their beliefs; if there is any situation that would lead you to conclude that it's not Friday, then that would suffice to prove that your mind's internal probability is not Friday.
Most of the time, when people talk about probabilities or state the probabilities they assign to something, they're talking about loose, verbal estimates, which are created by their conscious minds. There are various techniques for trying to make these match up to the evidence the person has, but in the end they're still just basically guesses at what's going on in your subconscious. Your conscious mind is capable of assigning probabilities like 0.999999999.
Taking a (modified) page from Randaly's book, I would define absolute certainty as "so certain that one cannot conceive of any possible evidence which might convince one that the belief in question is false". Since you can conceive of the brain-in-the-vat scenario and believe that it is not impossible, I would say that you cannot be absolutely certain of anything, including the axioms and logic of the world you know (even the rejection of absolute certainty).
I don't have to believe that the alternatives are impossible; I just have to be certain that the alternatives are not exemplified.
Is someone absolutely certain if the say that they cannot imagine any circumstances under which they might change their beliefs (or, alternately, can imagine only circumstances which they are absolutely certain will not happen)? It would seem to be a better definition, as it defines probability (and certainty) as a thing in the mind, rather than outside.
In this case, I would see no contradiction as declaring someone to be absolutely certain of their beliefs, though I would say (with non-absolute certainty) that they are incorrect. Someone who believes that the Earth is 6000 years old, for example, may not be swayed by any evidence short of the Christian god coming down and telling them otherwise, an event to which they may assign 0.0 probability (because they believe that it's impossible for their god to contradict himself, or something like that).
Further, I would exclude methods of changing someone's mind without using evidence (surgery or cosmic rays). I can't quite put it into words, but it seems like the fact that it isn't evidence and instead changes probabilities directly means that it doesn't so much affect beliefs as it replaces them.
Disagree. This would be a statement about their imagination, not about reality.
Also, people are not well calibrated on this sort of thing. People are especially poorly calibrated on this sort of thing in a social context, where others are considering their beliefs.
ETA: An example: While I haven't actually done this, I would expect that a significant fraction of religious people would reply to such a question by saying that they would never change their beliefs because of their absolute faith. I can't be bothered to do enough googling to find a specific interviewee about faith who then became an atheist, but I strongly suspect that some such people actually exist.
Yeah, fair enough.
You are correct. I am making my statements on the basis that probability is in the mind, and as such it is perfectly possible for someone to have a probability which is incorrect. I would distinguish between a belief which it is impossible to disprove, and one which someone believes it is impossible to disprove, and as "absolutely certain" seems to refer to a mental state, I would give it the definition of the latter.
(I suspect that we don't actually disagree about anything in reality. I further suspect that the phrase I used regarding imagination and reality was misleading; sorry, it's my standard response to thought experiments based on people's ability to imagine things.)
I'm not claiming that there is a difference between their stated probabilities and the actual, objective probabilities. I'm claiming that there is a difference between their stated probabilities and the probabilities that they actually hold. The relevant mental states are the implicit probabilities from their internal belief system; while words can be some evidence about this, I highly suspect, for reasons given above, that anybody who claims to be 100% confident of something is simply wrong in mapping their own internal beliefs, which they don't have explicit access to and aren't even stored as probabilities (?), over onto explicitly stated probabilities.
Suppose that somebody stated that they cannot imagine any circumstances under which they might change their beliefs. This is a statement about their ability to imagine situations; it is not a proof that no such situation could possibly exist in reality. The fact that it is not is demonstrated by my claim that there are people who did make that statement, but then actually encountered a situation that caused them to change their belief. Clearly, these people's statement that they were absolutely, 100% confident of their belief was incorrect.
I would still say that while belief-altering experiences are certainly possible, even for people with stated absolute certainty, I am not convinced that they can imagine them occurring with nonzero probability. In fact, if I had absolute certainty about something, I would as a logical consequence be absolutely certain that any disproof of that belief could not occur.
However, it is also not unreasonable that someone does not believe what they profess to believe in some practically testable manner. For example, someone who states that they have absolute certainty that their deity will protect them from harm, but still declines to walk through a fire, would fall into such a category - even if they are not intentionally lying, on some level they are not absolutely certain.
I think that some of our disagreement arises from the fact that I, being relatively uneducated (for this particular community) about Bayesian networks, am not convinced that all human belief systems are isomorphic to one. This is, however, a fault in my own knowledge, and not a strong critique of the assertion.
First, fundamentalism is a matter of theology, not of intensity of faith.
Second, what would these people do if their God appeared before them and flat out told them they're wrong? :-D
Clearly they would consider this entity a false God/Satan.
This is starting to veer into free-will territory, but I don't think God would have much problem convincing these people that He is the Real Deal. Wouldn't be much of a god otherwise :-)
That's vacuously true, of course. Which makes you original question meaningless as stated.
It wasn't so much meaningless as it was rhetorical.
Fixed, thanks.
Their verbal response would be that this would be impossible.
(I agree that such a situation would likely lead to them actually changing their beliefs.)
At which point you can point out to them that God can do WTF He wants and is certainly not limited by ideas of pathetic mortals about what's impossible and what's not.
Oh, and step back, exploding heads can be messy :-)
This is not the place to start dissecting theism, but would you be willing to concede the possible existence of people who would simply not be responsive to such arguments? Perhaps they might accuse you of lying and refuse to listen further, or refute you with some biblical verse, or even question your premises.
Of course. Stuffing fingers into your ears and going NA-NA-NA-NA-CAN'T-HEAR-YOU is a rather common debate tactic :-)
Don't you observe people doing that to reality, rather than updating their beliefs?
That too. Though reality, of course, has ways of making sure its point of view prevails :-)
This is not an accurate representation of mainstream theology. Most theologists believe, for example, that it is impossible for God to do evil. See William Lane Craig's commentary.
First you mean Christian theology, there are lot more theologies around.
Second, I don't know what is "mainstream" theology -- is it the official position of the Roman Catholic Church? Some common elements in Protestant theology? Does anyone care about Orthodox Christians?
Third, the question of limits on Judeo-Christian God is a very very old theological issue which has not been resolved to everyone's satisfaction and no resolution is expected.
Fourth, William Lane Craig basically evades the problem by defining good as "what God is". God can still do anything He wants and whatever He does automatically gets defined as "good".
I cannot imagine circumstances under which I would come to believe that the Christian God exists. All of the evidence I can imagine encountering which could push me in that direction if I found it seems even better explained by various deceptive possibilities, e.g. that I'm a simulation or I've gone insane or what have you. But I suspect that there is some sequence of experience such that if I had it I would be convinced; it's just too complicated for me to work out in advance what it would be. Which perhaps means I can imagine it in an abstract, meta sort of way, just not in a concrete way? Am I certain that the Christian God doesn't exist? I admit that I'm not certain about that (heh!), which is part of the reason I'm curious about your test.
If imagination fails, consult reality for inspiration. You could look into the conversion experiences of materialist, rationalist atheists. John C Wright, for example.
So you're effectively saying that your prior is zero and will not be budged by ANY evidence.
Hmm... smells of heresy to me... :-D
I would argue that this definition of absolute certainty is completely useless as nothing could possibly satisfy it. It results in an empty set.
If you "cannot imagine under any circumstances" your imagination is deficient.
I am not arguing that it is not an empty set. Consider it akin to the intersection of the set of natural numbers, and the set of infinities; the fact that it is the empty set is meaningful. It means that by following the rules of simple, additive arithmetic, one cannot reach infinity, and if one does reach infinity, that is a good sign of an error somewhere in the calculation.
Similarly, one should not be absolutely certain if they are updating from finite evidence. Barring omniscience (infinite evidence), one cannot become absolutely/infinitely certain.
What definition of absolute certainty would you propose?
So you are proposing a definition that nothing can satisfy. That doesn't seem like a useful activity. If you want to say that no belief can stand up to the powers of imagination, sure, I'll agree with you. However if we want to talk about what people call "absolute certainty" it would be nice to have some agreed-on terms to use in discussing it. Saying "oh, there just ain't no such animal" doesn't lead anywhere.
As to what I propose, I believe that definitions serve a purpose and the same thing can be defined differently in different contexts. You want a definition of "absolute certainty" for which purpose and in which context?
You are correct, I have contradicted myself. I failed to mention the possibility of people who are not reasoning perfectly, and in fact are not close, to the point where they can mistakenly arrive at absolute certainty. I am not arguing that their certainty is fake - it is a mental state, after all - but rather that it cannot be reached using proper rational thought.
What you have pointed out to me is that absolute certainty is not, in fact, a useful thing. It is the result of a mistake in the reasoning process. An inept mathematician can add together a large but finite series of natural numbers, and then write down "infinity" after the equals sign, and thereafter goes about believing that the sum of a certain series is infinite.
The sum is not, in fact, infinite; no finite set of finite things can add up to an infinity, just as no finite set of finite pieces of evidence can produce absolute, infinitely strong certainty. But if we use some process other than the "correct" one, as the mathematician's brain has to somehow output "infinity" from the finite inputs it has been given, we can generate absolute certainty from finite evidence - it simply isn't correct. It doesn't correspond to something which is either impossible or inevitable in the real world, just as the inept mathematician's infinity does not correspond to a real infinity. Rather, they both correspond to beliefs about the real world.
While I do not believe that there are any rationally acquired beliefs which can stand up to the powers of imagination (though I am not absolutely certain of this belief), I do believe that irrational beliefs can. See my above description of the hypothetical young-earther; they may be able to conceive of a circumstance which would falsify their belief (i.e. their god telling them that it isn't so), but they cannot conceive of that circumstance actually occurring (they are absolutely certain that their god does not contradict himself, which may have its roots in other absolutely certain beliefs or may be simply taken as a given).
:-) As in, like, every single human being...
Yep. Provided you limit "proper rational thought" to Bayesian updating of probabilities this is correct. Well, as long your prior isn't 1, that is.
I'd say that if you don't require internal consistency from your beliefs then yes, you can have a subjectively certain belief which nothing can shake. If you're not bothered by contradictions, well then, doublethink is like Barbie -- everything is possible with it.
Well, yes.
That is the point.
Nothing is absolutely certain.
Why does a deficient imagination disqualify a brain from being certain?
Vice versa. Deficient imagination allows a brain to be certain.
... ergo there exist human brains that are certain.
if people exist that are absolutely certain of something, I want to believe that they exist.
So... a brain is allowed to be certain because it can't tell it's wrong?
Tangent: Does that work?