Lewis and Anscombe on distinguishing "irrational" from "nonrational"

In my book and in my 1989 essay, "The Lewis-Anscombe Controversy: A Discussion of the Issues," I discussed Anscombe's insistence that Lewis distinguish between irrational causes and non-rational causes. Irrational causes would be things like being bitten by a black dog as a child gives you a complex and causes you to believe that all black dogs are dangerous. Nonrational causes are physical events or physical causes. Now interestingly enough, when I wrote a paper on Lewis on ethical subjectivism back in grad school I noticed this passage from Part I of The Abolition of Man:

Now the emotion, thus considered by itself, cannot be either in agreement or disagreement with Reason. It is irrational not as a paralogism is irrational, but as a physical event is irrational: it does not rise even to the dignity of error.

Now, in this passage doesn't Lewis draw the exact distinction on which Anscombe insisted? The only difference here is that Lewis distinguishes two senses of the term "irrational" instead of distinguishing between irrational and nonrational. But was Lewis's usage of the term "irrational" wrong? Going to a dictionary definition of "irrational" (see link below) I think not. Nevetheless, Lewis changed from "irrational" to "nonrational" to accomodate Anscombe's criticism.

This is the dictionary entry:

Dictionary.com Unabridged (v 1.0.1) - Cite This Source
ir‧ra‧tion‧al  /ɪˈræʃənl/ Pronunciation Key - Show Spelled Pronunciation[i-rash-uh-nl] Pronunciation Key - Show IPA Pronunciation

–adjective 1. without the faculty of reason; deprived of reason.
2. without or deprived of normal mental clarity or sound judgment.
3. not in accordance with reason; utterly illogical: irrational arguments.
4. not endowed with the faculty of reason: irrational animals.
5. Mathematics. a. (of a number) not capable of being expressed exactly as a ratio of two integers.
b. (of a function) not capable of being expressed exactly as a ratio of two polynomials.

6. Algebra. (of an equation) having an unknown under a radical sign or, alternately, with a fractional exponent.
7. Greek and Latin Prosody. a. of or pertaining to a substitution in the normal metrical pattern, esp. a long syllable for a short one.
b. noting a foot or meter containing such a substitution.

–noun 8. Mathematics. irrational number.


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[Origin: 1425–75; late ME < L irratiōnālis. See ir-2, rational]

—Related forms
ir‧ra‧tion‧al‧ly, adverb
ir‧ra‧tion‧al‧ness, noun


—Synonyms 3. unreasonable, ridiculous; insensate.
Dictionary.com Unabridged (v 1.0.1)
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006


In writing about this in my 1989 paper "The Lewis-Anscombe Controversy: A Discussion of the Issues," I conceded Anscombe's point but argued that since scientific knowledge depends crucially on our having knowledge that is inferred from other things we know, the distinction hardly sinks Lewis's argument. But I should have gone futher. The dictionary definition clearly shows that the word "irrational" can be used in both senses. Therefore any claim that Anscombe exposed a blunder on Lewis's part is clearly incorrect.

I am grateful to Jim Slagle for pointing this out.