Chesterton’s superb short study St. Thomas Aquinas: The Dumb Ox contains, among countless delights of reasoning and composition, a brilliant little discourse on Aristotelian induction compared to the modern reductionism that masquerades as an enthusiasm for induction. Its utility in dismantling that hectoring bluster, everywhere in evidence these days, which goes around with grandiose gestures toward certain collections of empirical data, in order to pronounce an important debate OVER, will be readily apparent.
I have never understood why there is supposed to be something crabbed or antique about a syllogism; still less can I understand what anybody means by talking as if induction had somehow taken the place of deduction. The whole point of deduction is that true premises produce a true conclusion. What is called induction seems simply to mean collecting a larger number of true premises, or perhaps, in some physical matters, taking rather more trouble to see that they are true. It may be a fact that a modern man can get more out of a great many premises, concerning microbes or asteroids, than a medieval man could get out of a very few premises about salamanders and unicorns. But the process of deduction from the data is the same for the modern mind as for the medieval mind; and what is pompously called induction is simply collecting more of the data. And Aristotle or Aquinas, or anybody in his five wits, would of course agree that the conclusion could only be true if the premises were true; and that the more true premises there were the better. It was the misfortune of medieval culture that there were not enough true premises, owing to the rather ruder conditions of travel or experiment. But however perfect were the conditions of travel or experiment, they could only produce premises; it would still be necessary to deduce conclusions. But many modern people talk as if what they call induction were some magic way of reaching a conclusion, without using any of those horrid old syllogisms. But induction does not lead us to a conclusion. Induction only leads us to a deduction. Unless the last three syllogistic steps are all right, the conclusion is all wrong. Thus, the great nineteenth century men of science, whom I was brought up to revere (“accepting the conclusions of science,” it was always called), went out and closely inspected the air and the earth, the chemicals and the gases, doubtless more closely than Aristotle or Aquinas, and then came back and embodied their final conclusion in a syllogism. “All matter is made of microscopic little knobs which are indivisible. My body is made of matter. Therefore my body is made of microscopic little knobs which are indivisible.” They were not wrong in the form of their reasoning; because it is the only way to reason. In this world there is nothing except a syllogism – and a fallacy. But of course these modern men knew, as the medieval men knew, that their conclusions would not be true unless their premises were true. And that is where the trouble began. For the men of science, or their sons and nephews, went out and took another look at the knobby nature of matter; and were surprised to find that it was not knobby at all. So they came back and completed the process with their syllogism. “All matter is made of whirling protons and electrons. My body is made of matter. Therefore my body is made of whirling protons and electrons.” And that again is a good syllogism; though they may have to look at matter once or twice more, before we know whether it is a true premise and a true conclusion. But in the final process of truth there is nothing else except a good syllogism. The only other thing is a bad syllogism; as in the familiar fashionable shape: “All matter is made of protons and electrons. I should very much like to think that mind is much the same as matter. So I will announce through the microphone or the megaphone that my mind is made of protons and electrons.” But that is not induction; it is only a very bad blunder in deduction. That is not another or new way of thinking; it is only ceasing to think.
What is really meant, and what is much more reasonable, is that the old syllogists sometimes set out the syllogism at length; and certainly that is not always necessary. A man can run down the three steps much more quickly than that; but a man cannot run down the three steps if they are not there. If he does, he will break his neck, as if he walked out of a fourth-story window. The truth about this false antithesis of induction and deduction is simply this; that as premises or data accumulated, the emphasis and detail was shifted to them, from the final deduction to which they lead. But they did lead to a final deduction; or else they led to nothing. The logician had so much to say about electrons or microbes that he dwelt most on these data and shortened or assumed his ultimate syllogism. But if he reasoned rightly, however rapidly, he reasoned syllogistically.
Nowhere is this lesson more wanting than the disputation over climate change. Not a day goes by where some mandarin or professor or politician fails to ensnare himself (and attempt to ensnare the rest of us) in the blunder laid out by Chesterton: piling up impressive data to form premises, but declining to demonstrate via syllogism the conclusion he assumes. It’s much more convenient and self-satisfying to mount a soapbox and cut loose with a sanctimonious harangue.