A lot of this depends on where you draw the line between ‘rationality’ and ‘science’ or ‘economics’ and ‘philosophy’ or so on. As well, given that ‘rationality’ is doing the best you can given the constraints you’re under, it seems likely that many historical figures were ‘rational’ even if they weren’t clear precursors to the modern rationalist cluster.
For example, I think Xunzi (~3rd century BCE) definitely counts; check out Undoing Fixation in particular. [His students Li Si and Han Fei are also interesting in this regard, but I haven’t found something by them yet that makes them clearly stand out as rationalists. Also, like JenniferRM points out, they had a troubled legacy somewhat similar to Alexander’s.]
Some people count Mozi as the ‘first effective altruist’ in a way that seems similar.
LaPlace is primarily famous as a mathematician and scientist, but I think he was important in the development of math underpinning modern rationality, and likely counts.
Benjamin Franklin seems relevant in a handful of ways; his autobiography is probably the best place to start reading.
Alfred Korzybski is almost exactly a hundred years older than Yudkowsky, and is the closest I’m aware of to rationality-as-it-is-now. You can see a discussion of sources between then and now in Rationalism Before The Sequences.
A lot of this depends on where you draw the line between ‘rationality’ and ‘science’ or ‘economics’ and ‘philosophy’ or so on. As well, given that ‘rationality’ is doing the best you can given the constraints you’re under, it seems likely that many historical figures were ‘rational’ even if they weren’t clear precursors to the modern rationalist cluster.
For example, I think Xunzi (~3rd century BCE) definitely counts; check out Undoing Fixation in particular. [His students Li Si and Han Fei are also interesting in this regard, but I haven’t found something by them yet that makes them clearly stand out as rationalists. Also, like JenniferRM points out, they had a troubled legacy somewhat similar to Alexander’s.]
Some people count Mozi as the ‘first effective altruist’ in a way that seems similar.
People point to Francis Bacon as the originator of empiricism; you can read his main work here on LW. While influential in English-language thought, I think he is anticipated by al-Haytham and Ibn Sina.
LaPlace is primarily famous as a mathematician and scientist, but I think he was important in the development of math underpinning modern rationality, and likely counts.
Benjamin Franklin seems relevant in a handful of ways; his autobiography is probably the best place to start reading.
Alfred Korzybski is almost exactly a hundred years older than Yudkowsky, and is the closest I’m aware of to rationality-as-it-is-now. You can see a discussion of sources between then and now in Rationalism Before The Sequences.