I don't have a lot to say about these next two paragraphs except that they demonstrate a level of education about logic that one rarely sees on display in modern writings (especially not in FB and blog comments):
Are you occasionally perturbed by the things written by adult men and women for adult men and women to read? We find a well-known biologist writing in a weekly paper to the effect that: "It is an argument against the existence of a Creator" (I think he put it more strongly; but since I have, most unfortunately, mislaid the reference, I will put his claim at its lowest)--"an argument against the existence of a Creator that the same kind of variations which are produced by natural selection can be produced at will by stock breeders." One might feel tempted to say that it is rather an argument for the existence of a Creator. Actually, of course, it is neither; all it proves is that the same material causes (recombination of the chromosomes, by crossbreeding, and so forth) are sufficient to account for all observed variations--just as the various combinations of the same dozen tones are materially sufficient to account for Beethoven's Moonlight Sonata and the noise the cat makes by walking on the keys. But the cat's performance neither proves nor disproves the existence of Beethoven; and all that is proved by the biologist's argument is that he was unable to distinguish between a material and a final cause. Here is a sentence from no less academic a source than a front- page article in the Times Literary Supplement: "The Frenchman, Alfred Epinas, pointed out that certain species (e.g., ants and wasps) can only face the horrors of life and death in association." I do not know what the Frenchman actually did say; what the Englishman says he said is patently meaningless. We cannot know whether life holds any horror for the ant, nor in what sense the isolated wasp which you kill upon the window-pane can be said to "face" or not to "face" the horrors of death. The subject of the article is mass behavior in man; and the human motives have been unobtrusively transferred from the main proposition to the supporting instance. Thus the argument, in effect, assumes what it set out to prove--a fact which would become immediately apparent if it were presented in a formal syllogism. This is only a small and haphazard example of a vice which pervades whole books--particularly books written by men of science on metaphysical subjects.
Words I never learned in school that Sayers uses with ease: final and material causes, syllogism, and supporting instance. (To give my university its due, I did learn about final causes in my colloquium on Western civilization.) I can't wait to study formal logic in a few years with my children!