The Codex

The Codex is a collection of essays written by Scott Alexander that discuss how good reasoning works, how to learn from the institution of science, and different ways society has been and could be designed. It also contains several short interludes containing fictional tales and real-life stories. The essays contained have been widely read within the rationality and effective altruism communities, and have a strong bias towards actually reading the scientific papers being discussed, analysing the arguments closely, and taking the conclusions seriously.

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Good and Bad Reasoning

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"The essay “How An Algorithm Feels From The Inside” is a gift that keeps on giving. You can get a reputation as a daring and original thinker just by copy-pasting it at different arguments with a couple of appropriate words substituted for one another, mad-libs like. It is the solution to something like 25% of extant philosophical problems."

73 min read

Nearly everyone is very very very overconfident. We know this from experiments where people answer true/false trivia questions, then are asked to state how confident they are in their answer. If people’s confidence was well-calibrated, someone who said they were 99% confident (ie only 1% chance they’re wrong) would get the question wrong only 1% of the time. In fact, people who say they are 99% confident get the question wrong about 20% of the time.

It gets worse. People who say there’s only a 1 in 100,000 chance they’re wrong? Wrong 15% of the time. One in a million? Wrong 5% of the time. They’re not just overconfident, they are fifty thousand times as confident as they should be.

57 min read

The Institution of Science

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Aquinas famously said: beware the man of one book. I would add: beware the man of one study.

For example, take medical research. Suppose a certain drug is weakly effective against a certain disease. After a few years, a bunch of different research groups have gotten their hands on it and done all sorts of different studies. In the best case scenario the average study will find the true result – that it’s weakly effective.

But there are also about 5 studies that find that the drug is very good, and 5 studies missing the sign entirely and finding that the drug is actively bad. There’s even 1 study finding that the drug is very bad, maybe seriously dangerous.

140 min read