Wednesday, October 06, 2010

On Bayesian subjectivism

JWL: Vic, if your "priors" are truly "priors" then they need to be there "prior."

So here you are wondering whether Christian theism is true. You were probably raised to believe in this Christian culture but now as the adult you have become you want to examine the case for yourself.

So when doing so what are your "priors" at that point? That is, what do you know and when? When do you place which "priors" into your bag of "priors"?


Name them in order to the best of your ability. And tell me how you arrived at them without using any subsequent ones.


VR: But the whole subjectivist theory of Bayesianism says that we best arrive at the truth if we conditionalize on the priors we have, since an arbitrary shift in priors won't be helpful in getting to the truth. If our priors are bad priors, then the evidence should move us off those priors to a more adequate belief system.

Bayesian subjectivism is a strongly anti-foundationalist theory of knowledge. I suppose it's a version of coherentism.

17 comments:

Doctor Logic said...

Victor,

I haven't been following along with JWL's argument, but I don't think we're talking about an arbitrary shift in the priors.

You don't get to stick with whatever crazy priors you started from. Uncritical beliefs aren't immune to criticism just because they were your initial beliefs. A prior is more than an initial belief.

It is well known that humans do not generally reach their inductive beliefs rationally. They sample non-randomly, they suffer confirmation bias, they remember recent results more prominently than results in the distant past, etc. The point is this: a man who has a million informal individual experiences does not typically have the inductive beliefs that he ought to have if he had used rigorous Bayesian methods. Instead, he typically has at least some beliefs that are extremely biased because he used a superstitious methodology.

So, when this man turns his mind to doing a Bayesian accounting of his beliefs, he can't simply treat his present beliefs as priors. He has to treat as his priors those beliefs he would have if he had done proper Bayesian accounting of his experiences all along.

In many cases, the person who uncritically accepts his superstitious beliefs as priors can eventually return to rational beliefs by using Bayesian inference and collecting more data.

However, when only a limited set of data is available, you can cripple your inferences. At the very least, you delay convergence.

Note that I'm not saying there's a solid foundation. Even using Bayesian methodology, there is plenty of subjectivity. There will be peculiarities, coincidences, and individual perspectives that shaped the observer's raw experiences. There will also be some variation in the theories each individual will come up with to explain the data.

Doctor Logic said...

There are two other errors I see Christians making in Bayesian inference.

First, we don't get to fine-tune theories for free.

Suppose that I believe that Elvis was a space alien. I then claim that sightings of Elvis after his death are not improbable because life after apparent death is not improbable for aliens. What's my error?

My error is that the theory that only Elvis was an alien is fine-tuned. My prior is ridiculous because there are at least a billion other priors (citing different individuals) I could have had in its place.

Why not MLK as the alien? Why not every second person? There are billions of alternate theories I could concoct, singling out past individuals (e.g., your grandmother) as aliens. Why pick Elvis as the one alien as my prior? It is at least as improbable that the one alien on Earth would choose the form of Elvis (out of all other individuals) as it is improbable that a human would be seen alive after death.

This is what Christian apologists do all the time. They say that resurrection is not improbable if Jesus is the son of God (false anyway, but that's another story). However, if God has one son, it is hyper-improbable that Jesus (out of the billions who have ever lived) is that one son. The only reason to bestow Jesus with that title (instead of, say, your grandmother) is that he was alleged to have come back from the dead. Well, that form of argument can be used to justify any belief, no matter how crazy. Why take "Jesus as son of God" to be your prior instead of "Carrot Top as son of God" as your prior? You don't get to be that arbitrary with your priors. That goes way beyond subjectivity.

The other error is that your own alleged Bayesian processes will never converge. To illustrate this, let me just ask you this question: "Assuming no more historical/archaeological evidence is discovered, should our belief that Abraham Lincoln was president of the United States be lower tomorrow? Or should it be higher or the same?

GREV said...

Hello:

I do not have the formal training in all the technical language that is often thrown around in some of these debates.

So, please bear with me.

Many people do not critically think about very much in their lives that is a given.

But can we posit as a given that a religous person, specifically a Christian theist is Always guilty of such an outlook?

I for one continue to view as entirely reasonable the case for Jesus on many grounds that I do believe involves thinking critically about the matter at hand.

Any priors that I might have had prior to conversion was an entirely social type gospel that minimized or even ridiculed actual belief in Jesus being who He claimed to be in the Christian Scriptures.


So my crazy priors were the priors of countless numbers of people, be a good person and you get to go to whatever heaven you think is there.

Not a robust superstitious methodology as far as I can see.

Yet all of that changed.

Because I was uncritcal in my acceptance of the claims of Christ?

Or .... was I persuaded that it does make sense and is reasonable in light of the evidence.

Just some thoughts as I read the claims of Doctor Logic.

Walter said...

GREV,

I don't have formal training either. I was raised to be a fundamentalist Baptist, so my "priors" are those of accepting that there is a creator of the universe who personally interacts with the created by revealing himself to certain prophets and disciples. Despite my priors I have come to the conclusion that the historical evidence for the miraculous claims in the New Testament is so weak that I am warranted in becoming agnostic about them ever having happened.

For the record, I am not a completely convinced naturalist, though I do lean towards naturalism. I am convinced that agnosticism is about as far as one can get without bolstering one's metaphysical beliefs with religious faith.

Doctor Logic said...

GREV,

Frequently, when I have exchanges about rational beliefs and critical thinking, people mistake me for saying something that I am not.

I'm not saying that you failed to put time and effort into your considerations about Christianity. I'm confident that most Christians on these forums second-guess themselves and spend a lot of time thinking about the questions. But dedication isn't what I'm talking about.

There are proper ways of reasoning and inferring truths from evidence. Humans are often quite bad at doing this, and human beliefs tend to deviate from what an ideal reasoner would conclude. When I say "think critically", I mean criticize your beliefs to ensure that they fall in line with what a proper reasoner would conclude. All the dedication in the world won't help me if I keep returning to irrational processes for forming beliefs.

Critical thinking isn't just a matter of thinking what-ifs or of maintaining angst about one's beliefs. There are methods to it.

GREV said...

Walter:

Many thanks for the comments you wrote.

I find it interesting that many who subscribe to atheism or agnosticism, once held "fundamentalist" beliefs. By ther own definition.

By my own definition I did not.

My journey has brought me to a place of subscribing more and more to what would be called the "New Reformed" outlook regarding Christian belief.

I am also a Pastor, serving 2 churches, and have been a pastor for over 20 years now.

I would argue that all beliefs are in some form or another religious in orientation and I belief that is a very defensible proposition.

The main text I cite in defence of such an idea is -- The Myth of Religious Neutrality" by Roy Clouser.

I do not yet claim great mastery of the ideas presented in the book. Rather a growing acquaintance with them.

A question for you is -- have you read -- The Devil's Delusion:Atheism and its Scientific Pretensions bu a fellow agnostic traveller -- David Berlinski?

Or have you read -- Naturalism: A critical analysis. Editors are Craig and Moreland and it is published by Routledge as part of their series on Twentieth Century Phlosophy. That book is very pricey!!!! Find it in a library.

I find the appeal of naturalism to be appealing but in the end lacking substance for the following reason posed by Berlinski:

"Beyond quantum cosmology and Darwinian biology — the halt and the lame — there is the solemn metaphysical aura of science itself. It is precisely the aura to which so many scientists reverently appeal. The philosopher John Searle has seen the aura. The “universe,” he has written, “consists of matter, and systems defined by causal relations.”

Does it indeed? If so, then God must be nothing more than another material object, a class that includes stars, starlets and solitons. If not, what reason do we have to suppose that God might not exist?

We have no reason whatsoever. If neither the sciences nor its aura have demonstrated any conclusion of interest about the existence of God, why then is atheism valued among scientists?....

By the same token, it requires no very great analytic effort to understand why the scientific community should find atheism so attractive a doctrine. At a time when otherwise sober individuals are inclined to believe that too much of science is too much like a racket, it is only sensible for scientists to suggest aggressively that no power exceeds their own."

Why shouldn't the scientific community find atheism so attractive a doctrine? It is only sensible for scientists to suggest aggressively that no power exceeds their own."


From -- The Scientific Embrace of Atheism
April 28, 2008 - by David Berlinski

Doctor Logic said...

GREV,

If I can summarize Bayesian reasoning in one sentence, it is this: account for false positives.

You ask (or is it Berlinski?) why scientists would be atheists. One big part of the answer is that they know that people would obtain beliefs in gods and supernatural events even if no god existed and no supernatural events occurred. For those things to be believed, we need extraordinary evidence because there's so much noise from false positives.

It's like asking a blindfolded man whether it's dark. Most of the time, he'll say yes, whether it's actually dark or not.

Also, atheism is poorly understood. An atheist is someone who does not positively believe in the existence of any gods. He will be atheist about some gods and agnostic about others. For example, everyone has to be agnostic about the god who leaves no trace of his existence. And everyone has to be hard atheist about the three-horned rhino god who makes his existence plain to everyone. A theist is someone who positively believes in one or more gods.

The evidence against the Abrahamic gods is overwhelming, IMO. I am a hard atheist about them. I am agnostic about gods of the deist variety.

Walter said...

The evidence against the Abrahamic gods is overwhelming, IMO. I am a hard atheist about them. I am agnostic about gods of the deist variety.

Ditto.

GREV said...

Doctor Logic:

Excellent paragraph --


-- There are proper ways of reasoning and inferring truths from evidence. Humans are often quite bad at doing this, and human beliefs tend to deviate from what an ideal reasoner would conclude. When I say "think critically", I mean criticize your beliefs to ensure that they fall in line with what a proper reasoner would conclude. All the dedication in the world won't help me if I keep returning to irrational processes for forming beliefs.--

Many questions come to mind.

Does a proper reasoner automatically assume that knowledge is only bounded by the material world and automatically exclude the non-material world? Hardcore materialism is not and has never been the majority viewpoint. Not to say that it might not be true, I would just believe that it has a longer road to go to prove its case when set over against the overwhelming spiritual impulse that undergirds so many. Without commenting on which idea of the spiritual is correct at this point.

So is an ideal reasoner an Enlightenment type of whatever shade we might want to posit? That claim to vest all proper ways of understanding in an Enlightenment type approach is questionable. Without dismissing the need to use reason. I just question the claim of some that reason is somehow infallible and never leads a person to irrationality in beliefs or practice.

IS there no such thing as spiritual knowledge? Is there evidence for spiritual knowledge and reasoning from spiritual knowledge? Responses in the negative seem to assume too much of an identification being mental process and physicality. The mental is not totally summarized by the physical processes.

That debate is not over and to just automatically assume so is I think problematic.
So, to retain a belief in the spiritual is not to base a person's thought processes in the irrational. I will grant it can lead to irrational behaviour. But it is not a given that all religious people are irrational.

I aim none of these questions at anyone. Just pondering and what I am pondering might be worthless.

Doctor Logic writes -- “The evidence against the Abrahamic gods is overwhelming, IMO. I am a hard atheist about them. I am agnostic about gods of the deist variety.”

Several responses come immediately to mind. It does a disservice to the discussion to the Jewish, Moslem and Christian believer to posit gods when speaking of the Abrahamic monotheistic religious viewpoint.

All of these religious traditions posit the idea of One Supreme Being. That needs to be a minimum for any further discussion on that to proceed. Yes there are streams within Christianity that believe in certain ideas regarding Jesus. But it remains that for the vast majority of Christian believers God is One and the mystery of the Trinity is what it is. A statement of fact that does not yield to a complete rationalistic attempt at understanding. It does not mean it cannot be rational.

A deist type god is essentially a god of convenience and thus not very convincing or worthy of much that would approach belief. I would much rather grapple with a God who demands much of me, then a deist god who leaves me alone to my own devices.

Have a great day

Walter said...

A deist type god is essentially a god of convenience and thus not very convincing or worthy of much that would approach belief. I would much rather grapple with a God who demands much of me, then a deist god who leaves me alone to my own devices.

I am not sure that reality cares much for what we had "rather" believe in or grapple with. I would rather believe in the truth versus what I find emotionally comfortable. I find little evidence for an intervening God. If there is a creator-deity, it does not seem to interject itself into human affairs in any manner that I can detect from my current perspective.

IS there no such thing as spiritual knowledge? Is there evidence for spiritual knowledge and reasoning from spiritual knowledge?

How can a person know if he is receiving a revelation from the "spirit" realm versus something self-generated from his own imagination?

Doctor Logic said...

GREV,

Does a proper reasoner automatically assume that knowledge is only bounded by the material world and automatically exclude the non-material world?

Not at all. I don't care whether causes are material or non-material. What does matter is the ability to detect our own errors and delusions.

The problem with theism isn't that it has non-material causation. The problem with theism is that God acts in ways indistinguishable from his non-existence.

When you take precautions to avoid human bias (i.e., by doing scientific testing), God vanishes. Are we really supposed to believe that the kind of God who exists is the kind who looks like he doesn't exist? The kind who is too afraid to appear to us in experimental tests?

Science isn't limited to the material. The proposition that God strikes-down blasphemers with lightning bolts is both non-physical and testable. God's will overrides physics, but it's still regular.

Another example: if God preferentially saved the lives of his followers, or made them resistant to disease, etc., that's a scientific, testable claim, even if the cause is non-material.

As it turns out, there is no evidence for anything more than material causation and human bias.

I also think that evolution implies (with high probability) that there is no designer. So, if a God does exist, he's not likely to be the kind to care about our existence. That pretty much rules out the Abrahamic religions.

Spiritual knowledge? No. There is no evidence that anyone has or has ever had spiritual knowledge of anything. There's no evidence that intuition is better than guessing, and it's often worse. In fact, every claim that has been tested to a conclusion has turned out to be a case of fraud or self-delusion. This doesn't stop people from making buck selling their "spiritual knowledge" to others. They usually get away with it because their "spiritual knowledge" is about stuff that isn't testable.

Rasmus Møller said...

Dr. Logic

- you may dismiss the evidence (such as the Bible and the witness of believers etc.) but evidence it is.

Very conveniently for my faith, I believe that God at present intends to win my heart, not my intellect, in order to change my character and personality; so that I become someone for whom eternal life is a blessing.

I believe He will eventually prove his existence and power scientifically for everyone. I tremble with joy and fear at the thought of that last day.

He is acting in love to make us love and trust Him freely, not to make us serve Him like a tyrant or manipulate him as a scientific object.

Doctor Logic said...

Rasmus,

Very conveniently for my faith, I believe that God at present intends to win my heart, not my intellect

Yeah, that's extremely convenient. It's also the only choice you have if you want to believe in God in the absence of evidence that would satisfy the intellect.

In other words, even if God doesn't exist, you've trapped yourself into the same belief condition.

He is acting in love to make us love and trust Him freely, not to make us serve Him like a tyrant or manipulate him as a scientific object.

What's tyrannical about letting us know of his existence? If following God is a good idea when we are unsure of his existence, why is it a bad idea when we are certain of his existence?

Just to illustrate... suppose that God does prove his existence and his all-powerful nature. How will you feel about him then? Will you still love him? Will you consider him a tyrant? If you will still love him even when you are certain of his existence, why shouldn't we all love him if he shows himself now?

Rasmus Møller said...

DL,

Work is killing me today, and it's our wedding anniversary. Hope to answer you Saturday.

brgds Rasmus

GREV said...

Doctor Logic:

I admire the confidence of your assertions.

Don't agree with them but I am glad you are confident in this stuff. Keith Ward, in a wonderful little work deals with some of these assertions and I will be borrowing from him when I do respond to name one of the authors I will use.

Hope to get at answering some of them perhaps after Canadian Thanksgiving -- this weekend -- and some other issues that I have to deal with.

Regards

Doctor Logic said...

Happy Anniversary, Rasmus!

Rasmus Møller said...

DL: Yeah, that's extremely convenient. It's also the only choice you have if you want to believe in God in the absence of evidence that would satisfy the intellect.

Rasmus: Oh but the the evidence does satisfy my meager intellect.

DL: In other words, even if God doesn't exist, you've trapped yourself into the same belief condition.

Rasmus: Well all beliefs may look like traps to those not sharing them. It could be worse; I could be trapped in a physicalist belief condition :)

DL: What's tyrannical about letting us know of his existence? If following God is a good idea when we are unsure of his existence, why is it a bad idea when we are certain of his existence?

Rasmus: He has let us know of His existence in number of ways already - first and foremost in Christ. For the kind certainty you demand, I think nothing less than the Apocalypse will suffice - and then it will be too late. You can't have Him on your own terms - only on His terms will eternity be Heaven for us.

DL: Just to illustrate... suppose that God does prove his existence and his all-powerful nature. How will you feel about him then? Will you still love him? Will you consider him a tyrant? If you will still love him even when you are certain of his existence, why shouldn't we all love him if he shows himself now?

Rasmus: If He showed only His existence and power, I would very much doubt that it was really Him. I love Him because He loved me first - I would know Him by His love. It is important we let the love relation with Him be restored, before He reveals Himself fully. We must want Him for His own sake, not for profit or self-preservation.

DL: Happy Anniversary, Rasmus!

Rasmus: Thanks a lot :)