Apologies for coming to this party a bit late. Particularly as I find my own answer really, really frustrating. While I wouldn't say it was an origin per se, getting into reading Overcoming Bias daily a few years back was what crystallised it for me. I'd find myself constantly somewhere between "well, yeah, of course" and "ohhhhhhhhhhhhhhh!" Guess the human brain doesn't tend to do Damascene revelations. We need overwhelming evidence, over a long period of time, to even begin chipping away at our craziest beliefs, and even then it's a step-by-step process.

The analogy I sometimes go over is something most people find fairly obvious like egalitarianism. You don't find many people who would attest to being pro-inequality. But all the same, you find very few people who have genuinely thought through what it means to be in favour of equality and really try to fit that into everyday life. The first step to becoming a rationalist is to admit how irrational everyone is without monumental efforts to the contrary.

BTW, I am totally on the road to de-Catholicising my mother. This is on the order of converting Dubya to Islam, so if I can manage that I'm awarding myself an honorary brown belt.

If by "rationalist", the LW community means someone who believes it is possible and desirable to make at least the most important judgements solely by the use of reason operating on empirically demonstrable facts, then I am an ex-rationalist. My "intellectual stew" had simmered into it several forms of formal logic, applied math, and seasoned with a BS in Computer Science at age 23.

By age 28 or so, I concluded that most of the really important things in life were not amenable to this approach, and that the type of thinking I had learned was useful for earning a living, but was woefully inadequate for other purposes.

At age 50, I am still refining the way I think. I come to LW to lurk, learn, and (occasionally) quibble.

Apologetics is a subset of theology, concerned strictly with justifying the tenets of the faith to doubters and nonbelievers.

Thomas Aquinas, by contrast, argued for the existence of God only briefly at the very beginning of the Summa Theologica, and devoted the rest to elucidating the properties of God, the other supernatural beings, and humanity. Much of theology is philosophy done with some particular background assumptions; apologetics is argument and rhetoric in defense of those assumptions.

ETA: In the modern world, most of the positive arguments for the existence of God are (of course) fatally flawed. The older "mainline" denominations realize this on some level and have essentially fallen back to the position "You can't know that there's not a God", which is something of a defense against losing one's own faith but not a great opening gambit for winning converts. The newer Protestant denominations aren't generally aware of the flaws in their arguments, and so use them to win converts.

In particular, the mainline denominations (and their theologians) shy away from empirical tests, while the newer denominations (and their apologists) embrace bad empirical tests. This is of course an oversimplification, but it's generally true.

It might strike people as odd, though, that most or at least half of those quotes come from books arguing for Catholicism. (They're really good! Can LessWrong start a Chesterton-is-awesome meme maybe?)

Cowen's talk reminds me of something C.S. Lewis mentioned in one of his books (perhaps it was "Miracles"): what he called, "picture-thinking".

Lewis noted that when we think about God, for example, many people will think of a kindly old, Caucasian man with a long white beard, sitting in a chair somehow anchored among fluffy white clouds. They will do this even though they know that God is invisible, certainly not male, nor Caucasian.

Lewis' point was that it's OK to have the picture in your head, as long as you know it is not literally true. We can posit that the picture may be true and useful in certain other respects (for example, for teaching that God wants to love and be loved as a "father", and that the kindly old man with the beard image helps us remember that).

The same should be applied to any stories; it ought to be OK to mentally organize certain of our mental storehouse of facts and opinions by telling ourselves stories, just as long as we don't mistake the story for "the whole enchilada", nor categorically rule out some story which, on the surface, appears to conflict with it.

Just as a good artisan or technician has a well-stocked toolbox and selects his tool with forethought and uses it with care, the intellectually well-stocked thinker uses multiple tools, ideally in a conscious way.