Friday, April 5, 2019

The What and Why of Logic

Classical education can be thought of as unique both in how it teaches things but also in what it teaches. The subject of Logic is one of those subjects that is unfortunately not found in most schools today, but it is one of the most foundational subjects to a classical education. Given everything else there is to study, why should we spend time on logic? Why not just take more time to study chemistry or literature? 

Logic is the science of good reasoning. It can be thought of as the language of truth. It is the study of proper inference. When someone reasons from a proposition (for example, that ‘God has commanded all men everywhere to repent) to the further proposition that they, indeed, are a man, and therefore should repent, they are being logical. When someone, however, reasons that because an unborn baby is composed of a bunch of cells, it is, therefore, nothing more than a bunch of cells, that person commits the fallacy of composition and reasons illogically. The term logic may sound grey, lifeless, or cold, but it undergirds the arguments of the colorful, the lively, and the emotional human beings made in God’s image. 

Formal logic, such as categorical logic, helps us sort things into proper categories and examine their relationships, such as the syllogism:

All men are mortal
Socrates is a man
Socrates is a mortal

Informal logic helps us see the issues of relevance or ambiguity in everyday arguments, such as the Ad Hominem, or attack on the irrelevant character of the person, rather than the soundness of the argument:


“Ben’s argument about taxes sounds reasonable, but he often yells at his wife, so we shouldn’t take it seriously."

We should study logic because in doing so we can be more human. Part of what it means to be human is to be logical. God created man with the ability to reason. When we reason, we apprehend the truth. This ability allows us to understand rational statements made by others, and to form rational statements ourselves and communicate them. 

The laws of logic actually undergird all communication, and without them, communication becomes impossible. Try making a statement without using the first law of logic, which is that A cannot equal non-A at the same time. Whatever you said, I could easily assert that you said the opposite, unless we both assume the first law of logic. A line can be either curved or straight, but the straight part cannot also be curved. When we make a statement like “the first twelve feet of this line is straight, and the last seven are curved,” we are in fact putting different propositions into categories, and because of the first law of logic mentioned above, when two categories are non-exclusive, they cannot have multiple meanings. We recognize this, and sort things into categories all of the time. When we get up in the morning, we decide to put on our snow boots rather than our flip-flops, and we understand that “snow boot” and “flip-flop” are exclusive items that cannot be the same thing. We then walk into the kitchen and make a distinction between a bowl and a counter, and conclude that based on the construction of those items, we should pour our milk into the bowl instead of next to it. Toddlers sometimes have trouble making these categorical distinctions. 

Perhaps the biggest reason to study logic is to obey the commands of Christ. Jesus Christ is described for us in John 1 as the Truth. In him is perfect and consistent reasoning. He does not think illogically, because He is perfectly truthful. Reasoning improperly is basically lying about reality. When you assert that because both Hitler and your political opponent love dogs, and that this means that they share political views, you are not merely reasoning illogically, but are in fact lying. Jesus does not lie, He commands His followers not to lie; instead He commands them to become like himself. We are commanded to conform to the image of Christ (Romans 8:29). We are also commanded to tear down every argument raised against the knowledge of Christ (1 Corinthians 10:5) and discern between (sort!) good and evil (Hebrews 5:14). 

In a classical school, logic is treated as a distinct discipline because it is of foundational importance, like reading. We teach people how to read because doing so allows them to interpret their world, obey God by reading his Word, and learn any other subject that requires reading. In the same way, we teach logic as a distinct discipline so that the student can interpret their world better, sorting between good and evil, true and false, helpful and unhelpful. By learning logic they will also be able to rightly interpret/exposit God's word after reading it. Lastly, by learning logic, the student will be able to interpret everything else they study! If you want a better math, science, literature, and rhetoric student, teach them how to interpret and sort between propositions in all of those subjects. 

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