This post reminds me of evidential markers in linguistics (http://en.wikipedia.org/wiki/Evidentiality). Evidential markers are morphemes (e.g. prefixes or suffixes) which, when attached to the verb, describe how the speaker came to belief the fact that he is asserting. These can include things like direct knowledge ("I saw it with my own eyes"), hearsay ("Somebody told me so but I didn't see for myself"), and inference ("I concluded it from my other beliefs"). While evidential markers are less specific than what's described in this post ("Somebody told me" rather than "John told me last Thursday at lunch"), I suspect that speakers of languages with evidential markers would be a lot more inclined to remember the more specific details.*
Does anyone here speak a language with evidential markers? If so, what do you think of the claim (asserted in at least four separate comments here) that these things would be far too difficult to remember and keep track of?
*I suspect this because I've read some articles about languages which use absolute direction (north, south, east, west) instead of subjective direction (left, right, in front of, behind); speakers of these languages develop very good internal compasses and always know which direction they're facing. (Here I'm assuming this is due to nurture rather than nature.) If language can cause people to acquire such a skill, it doesn't seem unreasonable that language could also cause people to acquire a talent for remembering sources of information.
This is my attempt to provide examples and a summarised view of the posts on "Against Doublethink" on the page How To Actually Change Your Mind.
What You Should Believe
Lets assume I am sitting down with my friend John and we each have incomplete and potentially inaccurate maps of a local mountain. When John says "My map has a bridge at grid reference 234567", I should add a note to my map saying "John's map has a bridge at grid reference 234567" *not* actually add the bridge to my map.
The same is true of beliefs. If Sarah tells me "the sky is green" I should, assuming she is not lying, add to my set of beliefs "Sarah believes the sky is green". What happens too often is that we directly add "The sky is green" to our beliefs. It is an overactive optimisation that works in most cases but causes occasional problems.
Taking the analogy a step further we can decide to question John about why he has drawn the bridge on his map. Then, depending on the reason, we can choose to draw the bridge on our map or not.
We can give our beliefs the same treatment. Upon asking Sarah why she believed the sky is green, if she said "someone told me" and couldn't provide further information I wouldn't choose to believe it. If, however, she said "I have seen it for myself" then I may choose to believe it, depending on my priors.
I Believe You Believe
The curious case is when someone says "I believe X". This can be meant a few ways:
The first case I do not have a problem with. It means your probability density has not yet shown a clear winner but you are giving me the answer that is in the lead at the moment. In this case I should add a note saying "You believes there is a bridge here, you are not very confident in the belief".
I don't have a problem with the second case either. I can have the belief "Angelina Jolie is attractive", someone else not have that belief, and we both be rational. This is because we are using different criteria for attractive. If I were to change it to a consistent definition of attractive it wouldn't be a problem e.g. The phrase "Angelina Jolie is regularly voted in the top 100 most attractive people in the world" doesn't require the phrase 'I believe...'.
The last case is even more curious. Lets assume that John (from our first example) says "I believe there is a bridge at grid reference 234567" but means it in the third case. I should add a note to my map saying "John has the following note on his map: 'I believe there is a bridge at grid reference 234567'". You would hope that the reason he has that note is because there is actually a bridge on his map. Unfortunately people are not that rational. You can have a cached belief that says "I believe X" even if you do not have "X" as a belief. By querying why they have that belief you should be able to work out if you should believe it, or even if they should.
To use the example from religion you can have the belief "I believe god exists" even if you do not have the belief "god exists".
Recommendations
I'm going to put myself on the line and give some recommendations: