Category Archives: Why learn logic?

A real-life enthymeme

Mr. Nance,

An article included said of the following argument, “That’s a syllogism without a minor premise”:

“[P]olitical decisions in the modern world often concern how to deploy science and technology, so people well-trained in science and technology will be better prepared to make those decisions.”

I would like to give this to my students to work on, but I can’t seem to translate Jacob’s rendering into terms that work formally. Do you have time to take a look?

All the Best. Continue reading A real-life enthymeme →

One Lesson Logic Students Must Learn!

Intermediate Logic, Introductory Logic, Why learn logic?, ,

The most important concepts to understand in Formal Logic is the concept of validity. All logic students should memorize and come to understand these three different (but related) ways of defining validity:

  1. In a valid argument, the premises imply the conclusion
  2. In a valid argument, if the premises are true, then the conclusion must be true.
  3. If an argument has true premises and a false conclusion, then it is invalid.

Continue reading One Lesson Logic Students Must Learn! →

The Dissection Lab & Logic

Logic, Why learn logic?,

Logic may be considered as a symbolic language which represents the reasoning inherent in other languages. It does so by reducing the language of statements and arguments down into symbolic form, simplifying them such that the arrangement of the language, and thus the reasoning within it, becomes apparent. The extraneous parts of statements are removed like a biology student in the dissection lab removes the skin, muscles and organs of a frog, revealing the skeleton of bare reasoning inside.

Continue reading The Dissection Lab & Logic →

Everything I say is a lie

Introductory Logic, Why learn logic?,

A statement is a sentence that has a truth value, either true or false. Several types of sentences are not statements – questions and commands, for instance – because they do not have truth values. Another type of sentence that is not a statement can be called nonsense.

Nonsense sentences are not statements for the same reason as questions and commands; they cannot be said to be true or false. There are two types of nonsense sentences that we usually encounter in studies of logic. Continue reading Everything I say is a lie →

Abstract Concrete

Introductory Logic, Poetics, Why learn logic?

One of my favorite college-level logic texts is The Art of Reasoning by David Kelley. In the chapter on “Classification” he teaches on genus and species, where he reminds us that the genus of a term is more abstract than the term itself, and the species of a term is more concrete.

Kelley includes an exercise for the students to practice with these concepts. He gives sentences for the students to rewrite, replacing any boldface words with more abstract ones, and any italicized words with more concrete ones. I thought this was a creative approach to teaching the concepts, so I thought I would come up with a few sentences for you to try:

  1. She likes to chitchat on her phone.
  2. The airplane plummeted into a field and crashed .
  3. I studied the sublime planet through an optical device.
  4. The person stuck his head through the bars and got stuck.
  5. He brought me to the banqueting house, and his banner over me was love.

Exercises like this can help us to understand the concepts of genus and species while developing creativity in writing. Try making up some of your own!

Genus & Species Bonus

Introductory Logic, Why learn logic?, ,

Lessons about genus and species charts often emphasize the capability of these charts to show relationships between terms (i.e. this is a kind of that). This is one benefit, but we should also note the benefit they provide in helping to develop arguments. Two classic examples should help to demonstrate this.

In C. S. Lewis’s The Lion, The Witch, and The Wardrobe, Susan and Peter are concerned with Lucy, who insists that she has gotten into the land of Narnia through a magic wardrobe. The Professor proceeds to develop an argument based off of this genus and species chart: Continue reading Genus & Species Bonus →

What will I learn in Logic?

Introductory Logic, Why learn logic?,

Logic-Bundle[1]The purpose of logic is to help students to be “masters of words in their intellects,” as Dorothy Sayers wrote, rather than “prey to words in their emotions.”

To this end, Introductory Logic teaches and trains students in four key skills: defining terms, making accurate statements, constructing arguments, and detecting fallacies in argument, the central concept being validity.

Learn logic in the younger years

Logic, Why learn logic?

“This habit of conceiving clearly, of judging justly, and of reasoning well, is not to be attained merely by the happiness of constitution, the brightness of genius, the best natural parts, or the best collection of logical precepts. It is custom and practice that must form and establish this habit… It is of infinite importance therefore, in our younger years, to be taught both the value and the practice of conceiving clearly and reasoning right.” – Isaac Watts