Reasons to Believe

Logic 101, Part 10 (of 12)

A student once said to me, "Hey prof, your logic class rocks!"

So to intentionally equivocate, it's not just geology courses that are known for "rocks."

In my twenty years of teaching college courses in philosophy and religion, the class students seem to appreciate most is Introduction to Logic. Students have often said that while they were initially nervous about taking a logic course, once in the class they soon felt empowered by studying the principles of sound reasoning.

Ordering one's thinking prepares a person to think rationally and critically about the important issues of life. And logic studies are an absolute essential for people who engage in the Christian apologetics enterprise.

Remember an argument consists of two essential parts: (1) a claim (or conclusion), and (2) support for the claim (or premises) in the form of reasons, evidence, or facts. A good argument (sound or cogent) requires that the premises genuinely support the conclusion.

Three Types of Logical Arguments

There are three important forms of reasoning or arguments with which students of logic should be familiar.

1.Deductive Arguments:

Deductive arguments are constructed in such a way as to produce conclusions that follow with certainty or with logical necessity from the premises. In a valid deductive argument, the reasoning process between the premises and conclusion is so well connected so as to guarantee or ensure the conclusion.

Here's an example of a particular type of deductive argument:

If Joan is a mother, then she must be a woman. Joan is a mother. Therefore, Joan is a woman.

2. Inductive Arguments:

Inductive arguments are constructed to produce conclusions that will probably follow from the premises. A strong inductive argument offers enough evidence to make the conclusion likely (or highly likely).

Here's an example of an inductive argument:

Voters in the state of Massachusetts predominantly vote for Democratic candidates over Republicans. Therefore, it's expected that the next U.S. senator elected in Massachusetts will be a Democrat.

3. Abductive Arguments:

Abductive arguments attempt to arrive at the best explanation for an event or a given series of facts. Unlike deduction, abduction provides no certainty in its conclusions but, like induction, yields more or less probable truth. In contrast to induction, however, abductive reasoning doesn't try to predict specific probable outcomes. Rather, this method tries to provide the best broad explanatory hypothesis. I use abductive reasoning in arguing that the best explanation of the life and ministry of Jesus Christ is that he was the divine Messiah (see chapter 8 of my book Without a Doubt: Answering the 20 Toughest Faith Questions).

These are the three basic types of reasoning (or arguments) found in the study of logic. If you would like to sharpen your own thinking skills, my critical thinking course is offered in Reasons Institute. (And I'm pleased to say it's the most popular class among the students.)

For more about the importance of logic and critical thinking, see my book A World of Difference: Putting Christian Truth-Claims to the Worldview Test. For a great handbook in dealing with logical fallacies, see Attacking Faulty Reasoning: A Practical Guide to Fallacy-Free Arguments by T. Edward Damer.


Part 1 | Part 2 | Part 3 | Part 4 | Part 5 | Part 6 | Part 7 | Part 8 | Part 9 | Part 10 | Part 11 | Part 12

Subjects: Logic

Kenneth R. Samples

I believe deeply that “all truth is God’s truth.” As an RTB scholar I have a great passion to help people understand and see the truth and relevance of Christianity’s truth-claims. Read more about Kenneth Samples.