11. Certainty. Logic has “outer limits”; thee are many things it can’t give you. But logic has no “inner limits”: like math, it never breaks down. Just as 2 plus 2 are unfailingly 4, so if A is B and B is C, then A is unfailingly C. Logic is timeless and unchangeable. It is certain. It is not certain that the sun will rise tomorrow (it is only very, very probable). But it is certain that it either will or won’t. And it is certain that if it’s true that it will, then it’s false that it won’t.
In our fast-moving world, much of what we learn goes quickly out of date. “He who weds the spirit of the times quickly becomes a widower,” says G.K. Chesterton. But logic never becomes obsolete. The principles of logic are timelessly true.
Our discovery of these principles, of course, changes and progresses through history. Aristotle knew more logic than Homer and we know more logic than Aristotle, as Einstein knew more physics than Newton and Newton knew more physics than Aristotle.
Our formulations of these changeless logical principles also change. This book is clearer and easier to read than Aristotle’s Organon 2350 years ago, but it teaches the same essential principles.
Our applications of the timeless principles of logic to changing things are also changing. The principles themselves are unchanging and rigid. They wouldn’t work unless they were rigid. When we hear a word like “rigid” or “inflexible,” we usually experience an automatic (“knee-jerk”) negative reaction. But a rigid a moment’s reflection should show us that, though people should not usually be rigid and inflexible, principles have to be. The wouldn’t work unless they were rigid. Unless the yardstick is rigid, you cannot use it to measure the non-rigid, changing things in the world, like the height of a growing child. Trying to measure our rapidly and confusingly changing world by a “flexible” and changing logic instead of an inflexible one is like trying to measure a squirming alligator with a squirming snake. [Adapted from Kreeft, Socratic Logic]