Rationalism should not be confused with rationality, nor with rationalization.

-Wikipedia article on rationalism 

I frequently see people using rationalism in place of rationality.  Usually other commenters understand them, however I believe that using the word rationality is superior.  The Less Wrong tag line is "A community blog devoted to refining the art of human rationality".  On the other hand, rationalism is the philosophical term for a very different epistemological position. Furthermore, -the -ism suffix has some undesirable connotations.  

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We use rationality and rationalist, the latter with a more or less specific meaning not used outside these circles. It's not a big leap to derive rationalism in the corresponding sense (i.e. the attitude of striving for improved rationality) from rationalist. I don't think this would be a huge problem, least of all internally. It's not like there's a big danger of mistaking anyone here for a rationalist in the traditional philosophical sense.

I haven't seen 'rationalism' used instead of rationality (on LW) more than once or twice. Don't get me wrong, if it were happening frequently I'd agree with the posting of this, but it seems to not be a very common problem to me.

It could just be that its one of my pet peeves, and thus I notice it more, but I see it very frequently. In fact I wrote this post because I wanted an easy reference instead of having to repeatedly retype my explanation every time I correct people. Sadly, Google is refusing only return results that include the exact string "rationalism", so I can't give exact numbers.

For exact match searches with Google, put the string in quotes.


For what it's worth, I've also quite often seen (and been mildly annoyed by) the same thing, mostly in Eliezer's writing. E.g., in phrases like "your strength as a rationalist".

If it weren't for the other meanings (denoting philosophical positions) the word has had, it would be quite a useful word to have -- a rationalist being someone who practises rationality, as a physicist is someone who practises physics and an artist someone who practises art. But, given the existence of those other meanings, in Eliezer's writing it's never perfectly clear when he means something like "person who practises rationality" and when he means something more like "person who gives precedence to rationality in all things". (One could argue that the two are the same thing, but they can't be made the same thing by definition, so it's better to have two words.)

(I don't think Eliezer ever uses the word with the older philosophers' meaning found in the SEP. -- reason versus sense-data, rather than reason versus unreason. To a good first approximation, neither does anyone who isn't a professional philosopher.)


Your claim seemed wrong to me, so I did a LW google search for "rationalism" and got 10 pages of results. There were about 13 results from 2013 (including this post.) I didn't look carefully but it seems at least a few of these incidents were using the word correctly. So with all the content posted on LW, "rationalism" is misused perhaps once every few weeks. It's basically a rare typo, not something worth a discussion post.


It may be rare, but it is certainly not only a typo; Eliezer in particular consistently uses the word with a meaning that is not a usual one.

I don't mean only that he doesn't use it with the traditional philosophical meaning that's opposed to "empiricism"; my impression is that usually (outside the writing of professional philosophers) it means something like "belief that reason in a broad sense is the only good way to seek truth". (The broad sense in question would include examination of empirical evidence, which is why this is not the traditional philosophical meaning.)

I'm all for rationalism in that sense, but I don't think that's how Eliezer usually uses the term; he seems to use it to mean something more like "the practice of rationality", and to use "rationalist" to mean "practitioner of rationality". Hence, e.g., the Sequence-post called "Your strength as a rationalist", and HPMOR!Harry's question to Draco along the lines of "Do you really think you're so good a rationalist that I should just trust what you say?", etc.

Rationalism would have been a good name if it wasn't already taken, since Eliezer's rationality is a philosophy among other things.

This is one of those things that frustrates me. There should be a nice concise word for the sorts of materials that are being collected on this site that doesn't require a ton of clarification, doesn't invoke whatever demons have caused 'rationalism' to be associated with anti-feminism in some circles, or suggest an innate contradiction with the useful pieces of empirical practice.

How many times in the past few months have I tried to express to someone, "I've been learning all sorts of interesting things about cognitive defects and undesirable human behavioral phenomena, applications of Bayes theorem, and other collected topics concerning epistemology in an effort to be less crazy, help others be less crazy, and be a more effective human" - or something along those lines? If for no other reason than brevity, I would love to have a word that helps succinctly express that, or something reasonably close to it, such that if you look into the word, you understand that it covers this type of interest.

Incidentally, if anyone can tell me what that "rationalism is anti-woman" thing is about, I'd really love to know. I don't see any particularly compelling reason that 'traditional rationalism' should be associated with anti-feminism (except as expressed by anti-feminists who also happened to subscribe to that philosophy, and even then, I don't know who those people are.)

Incidentally, if anyone can tell me what that "rationalism is anti-woman" thing is about, I'd really love to know. I don't see any particularly compelling reason that 'traditional rationalism' should be associated with anti-feminism (except as expressed by anti-feminists who also happened to subscribe to that philosophy, and even then, I don't know who those people are.)

Political interests do not have to be intrinsically opposed to have conflict. It is in the interests of feminism to target some territories in concept-space to colonize to further it's goals---such as asserting an epistemic fact about something to do with sex the belief of which will strengthen feminism. "Traditional rationalism" will also claim territories in such a way. When those claims overlap there is the potential for conflict. "Traditional rationalism" will have different priorities regarding assertions made on that subject than "feminism" and so the natural escalation for either side is to " are anti-".

It is not hard to think of examples of epistemic claims about subjects which would necessarily offend significant elements of one or the other of those groups but which are required by the other. Of course I will not give examples here because that will necessarily be offensive to at least one of said groups. (I support your-side.)

I only just understood this reply today. Thank you. (Edit: by which I mean, there are related lessons I learned today)

I think there are some useful distinctions one could draw here. Say:

  • Rationalism is the behavior; rationality is the effect.

  • Rationalism is the means; rationality is the end.

  • Rationalism is the community, the movement, the project; rationality is its object.

  • Rationalism is the body of teachings; rationality is the art it teaches.

I don't think there's a significant risk that historical rationalism (which isn't a particularly contentful doctrine in the first place) will get confused with what we're talking about. Maybe the -ism is harmful. Though there are innumerable cases where the utility of an -ism outweighs the cost. This might be a good place to fight the connotation.


There was a post 2.65 years ago making the same point: Note on Terminology: "Rationality", not "Rationalism".

Back then, the confusion between these terms seemed more salient, but Google results count doesn't support this impression (4.8% of "rationalism" in 2011 vs. 4.2% of "rationalism" in 2013). The result count from Jan 2011:

  • "rationality" - 3720 results
  • "rationalist" - 1210 results
  • "rationalism" - 251 results (4.8%)

Current results (Sep 2013):

  • "rationality" - 28400 results
  • "rationalist" - 3940 results
  • "rationalism" - 1410 results (4.2%)
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