Christianity drove me to rationalism. I went to a Catholic college where we had to take 2 semesters of theology and 3 semesters of philosophy.
We studied Aquinas for weeks. Knowing that Aquinas was generally regarded as the smartest person in the Middle Ages, I was stunned by the stupidity of his arguments. Aquinas could not have been stupid. Therefore, social pressure was capable of warping the minds of the smartest people on the planet for a thousand years. Therefore, it could be warping my mind right now.
Another thing we did was to study a parallel edition of the gospels. That means that it has one column each for Matthew, Mark, Luke, and John. Laying them out side-by-side, I saw many places where Matthew, Mark, and Luke had identical sentences. They couldn’t have come up with the same grammar and word choice independently. At least 2 of them had copied from someone else. I had studied the Bible all my life, and was surrounded by hundreds of people who also studied the Bible regularly. Some of them had read it every day for decades. And none of them had ever noticed this; or if they did, they didn’t mention it. (It is universally known to Biblical scholars; but most churches take a dim view of Bible scholars.) I realized that they couldn’t see it, no matter how smart they were or how much they read the Bible, because their preconceptions prevented them from looking for it.
I was astonished that most Christians have never read the entire Bible. If you believe that God wrote one book in which he said everything he wanted to say to the world, you would read that book. Yet even being aware of this, I found it hard to read. (To this day I suspect I may not have read Haggai.) I knew that this meant my rationality was broken (although at the time I attributed it to sin).
But now I remember an earlier event: I was about five. I was in the car, on a long trip with my family. Traffic stopped. There was an accident ahead. I saw a little dog walking away from the accident, down the road. I said that it was probably from one of the cars in the accident, and that I wanted to get out and pick it up before someone hit it. My parents said that was foolish, and that the dog could be dangerous. Then someone hit it. And I realized that I had been right—and that the fact that there were hundreds of grown-ups around me in their stopped cars, and none of them had done anything, didn’t mean a thing.
Mostly things that I’ve observed. For instance:
If you try to anticipate someone else’s misinterpretations of what you say, you are likely to match their reply to your expectations using regular-expression-like matching and reject their response, without fully parsing it.
Often, it’s better to say one insightful thing than to say one insightful thing and two less-insightful things, because the less-insightful things are easier to respond to.
Developing expertise in overcoming bias, and “trying really hard” to overcome bias, doesn’t overcome bias. It can make bias worse, by becoming an excuse not to update in response to the ideas of others.