No. He believes he has a proof now. But he said that he tried to build a proof because, before finding a proof, he believed there must be a proof - and it seems, from what he wrote, that he found the lack of such a proof offensive. That's faith.

The thought occurs to me that the converse question of "How do you know you're rational?" is "Why do you care whether you have the property 'rationality'?" It's not unbound - we hope - so for every occasion when you might be tempted to wonder how rational you are, there should be some kind of performable task that relates to your 'rational'-ness. What kind of test could reflect this 'rationality' should be suggested from consideration of the related task. Or conversely, we ask directly what associates to the task.

Prediction markets would be suggested by the task of trying to predict future variables; and then conversely we can ask, "If someone makes money on a prediction market, what else are they likely to be good at?"

Sorry, I said "Test the process, not the results", which is a strictly wrong misstatement. It is over-strong in the manner of a slogan.

A more accurate statement would be "Focus primarily on testing process, and secondarily on testing results."

Tsuyoku Naritai.

Interesting point. Does anyone know of any evidence about how well calibration test results match overconfidence in important real-life decisions? I'd expect it would give a good indication, but has anyone actually tested it?

Surely we want to distinguish "rational" from "winner." Are winners on average more rational than others? This is not clear to me.

ISO quality certification doesn't look primarily at the results, but primarily at the process. If the process has a good argument or justification that it consistently produces high quality, then it is deemed to be compliant. For example "we measure performance in [this] way, the records are kept in [this] way, quality problems are addressed like [this], compliance is addressed like [such-and-so]".

I can imagine a simple checklist for rationality, analogous to the software carpentry checklist.

1. Do you have a procedure for making decisions?
2. Is the procedure available at the times and locations that you make decisions?
3. How do you prevent yourself from making decisions without following this procedure?
4. If your procedure depends on calibration data, how do you guarantee the quality of your calibration data?
5. How does your procedure address (common rationality failure #1)?
6. et cetera

Sorry, it's just a sketch of a checklist, not a real proposal, but I think you get the idea. Test the process, not the results. Of course, the process should describe how it tests the results.

This is the fundamental question that determines whether we can do a lot of things - if we can't come up with evidence-based metrics that are good measures of the effect of rationality-improving interventions, then everything becomes much harder. If the metric is easily gamed once people know about it, everything becomes much harder. If it can be defeated by memorization like school, everything becomes much harder. I will post about this myself at some point.

This problem is one we should approach with the attitude of solving as much as possible, not feeling delightfully cynical about how it can't be solved, but at least you know it. It's too important for that. It sets up the incentives in the whole system. If the field of hedonics can try to measure happiness, we can at least try to measure rationality.

...but not to derail the discussion, Robin's individual how-do-you-know? stance is a valid perspective, and I'll post about the scientific measurement / institutional measurement problems later.

My family is Jewish and we all went to a Reform synagogue. This sect of Judaism is very liberal in the scheme of things, making it very clear that the bible is not literally true and accepting of just about anything, even agnosticism (if not atheism).

At the age of 16, Reform Judaism has a confirmation ceremony where one makes a statement of faith to the assembled congregation. I realized that I couldn't go up in front of a crowd and in good faith profess a belief in God. I had understood all of it to be just stories for a long time, at least since the age of 13, but I hadn't quite realized that meant I was an atheist. I just never really thought about it, but when I finally did it seemed obvious in retrospect. I ended up reading a poem to the congregation and it was very well received as it was the shortest speech given that day.

The next year, I decided I wasn't going to go to synagogue for the High Holidays (where my liberal synagogue had 3 hour long worship services). My parents weren't quite sure how to react, but they told my grandparents and my grandparents responded by deciding they weren't going either. This particular decision set off a chain reaction where it was determined that no one in my family from my grandparents on down were believers and we had all just been going along for each other's benefits. On the holidays now, my 92 year old grandfather always mentions how nice it is that the holidays give us reason to get the entire family together.