I teach logic online. In addition to my regular logic students I have several Classical Conversations tutors who audit my logic course. After I finish the lesson and my students leave, the auditors join the class live, turning on camera and mic, and we discuss the lesson. I appreciate these discussions, because I often learn as much from them as they do from me. Continue reading I Know London is the Capital of France

# Category Archives: Why learn logic?

# Shakespeare’s Use of the Liberal Arts: Logic

The classical Christian school movement is seeking to revive a form of education that helped shape some the greatest minds of western civilization. But how do we know that our father’s were trained according to the Trivium? One delightful demonstration of this is William Shakespeare’s frequent and detailed use of the liberal arts of grammar, logic and rhetoric in his plays and poems, a use thoroughly identified by Sister Miriam Joseph in her book *Shakespeare’s Use of the Arts of Language*. In this well-researched book, she argues that Shakespeare’s application of formal logic is evidenced in his use of definition, genus and species, syllogistic vocabulary, applied syllogisms, enthymemes, and more. Let me give some of her clearer examples. Continue reading Shakespeare’s Use of the Liberal Arts: Logic

# Relating Terms from Birmingham Jail

One practical method of organizing arguments is to identify relationships between terms. Terms may be related as different parts of a whole (including different steps in a process) or as different species of a genus. In his “Letter from Birmingham Jail” Martin Luther King Jr. uses both methods of relating terms to organize and clarify his arguments. Continue reading Relating Terms from Birmingham Jail

# Defining Terms from Birmingham Jail

A good introductory logic course will discuss the importance of defining terms in any argument. One clear demonstration of using definition in argument is Martin Luther King Jr.’s “Letter from Birmingham Jail,” a letter which King directed at Christian pastors in Alabama in 1963 defending his campaign of nonviolent direct action. Continue reading Defining Terms from Birmingham Jail

# Impressive Logic Students

Those who have taught a subject for many years have occasionally had the blessing of teaching a student who naturally has (or has developed) an intuitive insight into the subject. I was blessed this way by two of my logic students this morning!

I was teaching *Intermediate Logic*, Lesson 34, “Converting Truth Tables into Digital Logic Circuits.” We were going over the exercise, problem 3, for which the final answer in the text is the unsimplified proposition (~A • ~B • C) v (A • ~B • C). One of my students said, “I know that B has to be false and C has to be true, and it doesn’t matter about A. So that would simplify to ~B • C.” When I asked him if he has been reading ahead to future lessons, he said no, “I can just see it by looking at the proposition.” I was very impressed. He just saw future lessons on simplification techniques, without being taught them.

But the surprises for the morning were not yet over. Continue reading Impressive Logic Students

# Applying Intermediate Logic

The most recent edition of Intermediate Logic has two new sections, Unit 4 and Unit 5. I’ve included these new units in the text because I wanted to answer the important question, “What are some practical applications of the tools that we are learning about, i.e. truth tables, formal proofs, and truth trees?” I believe that the applications of these tools in the new units will deepen and solidify student understanding of the concepts that, up to that point, have been largely theoretical.

Unit 4 (Lesson 28) gives logic students the opportunity to analyze chains of reasoning. The arguments to be analyzed are taken from Boethius’s *The Consolation of Philosophy*, the Apostle Paul’s argument proving the general resurrection of the dead in I Corinthians 15, and a section on angelic will from Augustine’s *City of God*. I work through this last one in full on the DVD.

An exercise *not* in the text that may be beneficial would be to have students write their own chains of reasoning, arguing for a conclusion of their choosing, in imitation of these authors. Their arguments must include at least one NOT, AND, and OR, and two IF/THENs. Tell them to include a truth-table or truth-tree analysis of their own chain of reasoning.

Unit 5 (Lessons 29-40) teaches students how to apply what they have learned to the fascinating topic of Digital Logic. Do not be intimidated by the 0’s, 1’s, and new symbols. It’s just the same old true, false, and logical operators that they have already learned about presented in a new way. Students often find this a fun application of what they have learned. It helps them to understand the electronic world around them, and it shows that the tools that they have learned apply not only to philosophy and theology, but to digital clocks and iPhones!

# An exhortation to teachers regarding formal proofs

Formal proofs are hard, like many other things worth learning!

In this video, I talk through the difficulties of formal proofs of validity, and why it’s worth enduring the hardship to learn them.

YouTube version HERE.

# The Biblical Biconditional

Symbolic logic has five standard logical operators, each of which has a standard translation in English:

*negation* is “not”

*conjunction* is “and”

*disjunction* is “or”

*conditional* is “if/then”

*biconditional* is “if and only if”

While the translations of the first four logical operators are frequent in English, the phrase “if and only if” is used very infrequently, and then only occasionally among mathematicians, philosophers, and lawyers.

For instance, while it is easy to find hundreds of *not*s, *and*s, *or*s, and *if/then*s in the Bible, the phrase “if and only if” is completely absent. However, for those who look carefully, biconditional reasoning is used several times in scripture. Keeping in mind that *p if and only if q* means *if p then q and if q then p *— and remembering other equivalences we have learned — the following verses all reflect biconditional reasoning: Continue reading The Biblical Biconditional

# Help with Hypotheticals

One of the more practical parts of* Introductory Logic* is Lesson 31 on Hypothetical Syllogisms. Hypothetical syllogisms of all kinds are a very common form of reasoning, so we should not only be able to identify them quickly, but we should also learn to use the valid forms confidently.

A hypothetical statement is an “if/then” statement, such as this one: Continue reading Help with Hypotheticals

# 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