Program / Course 24: Apologetic Practicum / Lesson 1.1
What you will learn
- Identify the premises and the conclusion of an argument in ordinary speech and writing.
- Write an argument in standard form, one numbered line at a time.
- Explain the difference between a valid argument and a sound argument.
- Test an argument by asking whether its premises are true and whether the conclusion follows.
The big idea
An argument is not a quarrel. It is a set of statements in which some statements, the premises, are offered as reasons to accept another statement, the conclusion. A valid argument is one whose conclusion must be true if the premises are true. A sound argument is valid and also has true premises. Learning to see these parts is the first skill of apologetics, because a claim can only be defended, or fairly criticized, once its reasons are laid out where everyone can see them.
Key terms
- Argument
- A set of statements in which some (the premises) are given as reasons for accepting another (the conclusion).
- Premise
- A statement offered as a reason for the conclusion.
- Conclusion
- The statement an argument tries to show to be true.
- Valid
- Describing an argument whose form is such that, if the premises are true, the conclusion cannot be false.
- Sound
- Describing an argument that is valid and has only true premises.
- Cogent
- Describing an inductive argument whose premises are true and make the conclusion probable, though not certain.
- Deductive argument
- An argument meant to guarantee its conclusion if the premises are true.
- Inductive argument
- An argument meant to make its conclusion likely, not certain, often by pointing to evidence or patterns.
Background
The word apologetics comes from a Greek word, apologia, meaning a defense or a reasoned answer. The First Letter of Peter tells believers to be “ready always to give an answer to every man that asketh you a reason of the hope that is in you with meekness and fear” (1 Peter 3:15). A reason, in this sense, is not an emotion or a slogan. It is something that can be stated, examined and either accepted or challenged.
Logic is the study of what makes some reasons good and others poor. It was organized in the ancient world, most influentially by Aristotle, and Christian thinkers of every tradition have used it. Catholic scholastics such as Thomas Aquinas, Orthodox writers such as John of Damascus and Protestant theologians such as the authors of the Westminster Confession all argued in ways that can be set out in premises and conclusions. Logic does not belong to any one church. It is a shared tool.
Two cautions belong at the start. First, an argument is only one way to communicate. Prayer, testimony and poetry do not need to be turned into premises. Second, even a perfect argument does not by itself produce faith, and Christians differ on how much weight reasoning should carry. This course treats argument as a servant of honest speech, not as a replacement for the rest of the Christian life.
Step-by-step explanation
Step 1: Find the conclusion first
Ask: what is this person trying to get me to believe? That is the conclusion. Words such as therefore, so, thus and hence often point to it. Words such as because, since and for often point to a premise.
Take the sentence: “The tomb was empty, because the women found it so and no one produced a body.” The conclusion is that the tomb was empty. The rest are offered as reasons. Not every argument uses signal words, so read for the point first.
Step 2: List the premises
Write each reason as its own short, complete statement. Remove emotional language and repeated phrases. If one sentence holds two claims, split it into two premises.
Premises are not always stated. If a speaker says, “He is a priest, so he must be honest,” the unstated premise is something like “All priests are honest.” Naming such missing premises is the subject of the next lesson. For now, practice with arguments whose premises are visible.
Step 3: Write it in standard form
Standard form puts each premise on a numbered line and draws the conclusion below. A classic example is: (1) All men are mortal. (2) Socrates is a man. (3) Therefore, Socrates is mortal. Writing an argument this way makes it easy to point at the exact line you doubt.
A theological example: (1) Every event that begins to exist has a cause. (2) The universe began to exist. (3) Therefore, the universe has a cause. Whether this particular argument works is debated, and later lessons return to it. Here the point is only that it can be set out clearly.
Step 4: Test validity
An argument is valid when the conclusion follows from the premises by the form of the argument. To test it, suppose the premises are true and ask whether the conclusion could still be false. If it could, the argument is invalid.
Validity says nothing about whether the premises are true. “All cats are dogs; Felix is a cat; therefore Felix is a dog” is valid but absurd, because the first premise is false. And an argument can have true premises and still be invalid: “Some Christians are teachers; some teachers are poets; therefore some Christians are poets” does not follow.
Step 5: Test soundness and strength
A sound argument is valid and has true premises. If the argument is sound, its conclusion is true. This is why critics usually attack a premise, since attacking validity is harder once an argument is well formed.
Many arguments in religion and history are not deductive but inductive: they argue that a conclusion is probable. For these, ask whether the evidence is good, whether it is complete, and whether another explanation fits equally well. An inductive argument can be strong or weak, but it is not called valid or invalid.
- What exactly is the conclusion, stated in one sentence?
- Which statements are offered as reasons, and can each be written as its own premise?
- If every premise were true, would the conclusion have to be true, or only likely?
- Which premise would I doubt first, and what is my reason for doubting it?
- Is anything essential left unstated?
- Would the person who made this argument agree that I have stated it fairly?
Examples
A valid and sound argument
(1) Every human being will die. (2) Sam is a human being. (3) Therefore, Sam will die. The form is valid, and the premises are accepted by nearly everyone, so the argument is sound for practical purposes. (Constructed example.)
A valid but unsound argument
(1) Everyone who reads the Bible becomes perfectly kind. (2) Dana reads the Bible. (3) Therefore, Dana is perfectly kind. The form is valid, but the first premise is false, so the argument is not sound. (Constructed example.)
An invalid argument that sounds good
(1) If a church is faithful, it will be persecuted. (2) This church is being persecuted. (3) Therefore, this church is faithful. The conclusion does not follow. Persecution can have many causes, and the first premise does not say that only faithful churches are persecuted. (Constructed example.)
Different perspectives
Catholic thought
The Catholic tradition, following Aquinas and affirmed by the First Vatican Council, holds that human reason can know some truths about God. Arguments therefore have a real place in theology, though Catholics also hold that faith goes beyond what reason alone can prove.
Orthodox thought
Orthodox writers generally stress that God is known through worship and experience more than through proof. Many accept careful reasoning as useful, but they are wary of treating God as the conclusion of an argument, since God is not one object among others.
Protestant thought
Protestants disagree among themselves. Many evangelical apologists, such as William Lane Craig, defend formal arguments for God. Some Reformed thinkers, such as Alvin Plantinga, argue that belief in God can be reasonable without being based on an argument. Others in the Reformed tradition prefer to begin from Scripture and not from philosophy.
Secular and scholarly view
Philosophers of many outlooks agree on the basic vocabulary of premise, conclusion, validity and soundness. They disagree about whether the premises of religious arguments are true. Naming the parts clearly helps both sides locate that disagreement.
Why it matters
Most conversations about faith stall because the two speakers are not sure what is being claimed or why. Breaking an argument into parts replaces fog with specific questions. It also protects you from weak arguments you may like. A defender of the faith who cannot tell valid from invalid will eventually repeat a bad argument and embarrass the claim it was meant to serve.
Common misunderstandings
Misunderstanding: A valid argument is a true argument.
Correction: Validity only concerns the link between premises and conclusion. A valid argument with a false premise can have a false conclusion. Soundness requires validity and true premises.
Misunderstanding: If I cannot refute an argument, it must be sound.
Correction: Failure to find the flaw on the spot does not prove there is none. It may also mean you have not yet looked at the premises long enough. Slow down and write the argument out.
Misunderstanding: Using logic means not trusting Scripture or faith.
Correction: Writers in every Christian tradition have used logic in service of faith. Using careful reasoning is not a denial that faith, grace and worship matter.
Misunderstanding: Arguments are only for winning.
Correction: The purpose of an argument is to show why something is true. A good arguer is willing to learn that a premise is false.
Knowledge check
What is the difference between a premise and a conclusion?
A premise is a statement offered as a reason. The conclusion is the statement the reasons are meant to support. In a chain of reasoning, one conclusion can serve as a premise for the next step. To tell them apart, ask which statement the speaker is trying to persuade you to accept.
Can an argument be valid and still have a false conclusion?
Yes. If one of the premises is false, a valid argument can have a false conclusion. Validity guarantees only that true premises would give a true conclusion. This is why the next question after validity is always whether the premises are in fact true.
What does a sound argument require?
It requires two things: the argument must be valid, and every premise must be true. If both hold, the conclusion must be true. Because both are needed, critics may attack either the form of the argument or any single premise.
Why is an inductive argument not called valid?
An inductive argument only aims to make a conclusion probable, not certain. Validity means the conclusion is guaranteed by true premises, so the word does not fit. Inductive arguments are described instead as strong or weak, or cogent when strong and the premises are true.
Write a short argument of your own in standard form.
Answers will vary. A good answer has numbered premises, a clearly marked conclusion, and wording plain enough that someone who disagrees can say which line they reject. Example: (1) Promises should be kept. (2) I promised to help. (3) Therefore, I should help.
Think it through
- Think of a belief you hold firmly. Can you state it as a conclusion with premises? What happens when you try?
- Which is harder for you, noticing a false premise or noticing an invalid step? Why might that be?
- Why might some Christians, especially in Orthodox and some Protestant circles, be cautious about turning faith into the conclusion of an argument? Do you find their caution convincing?
- When did you last change your mind because of a reason someone gave you?
Independent assignment
Three arguments in standard form
In your own notebook, write 400 to 600 words. Choose three arguments from your reading, from a sermon or talk you remember, or from a conversation. Write each in standard form with numbered premises and a conclusion. For each, say whether it is valid, invalid or inductive, and name the premise you consider weakest. Then write a short paragraph on what you learned about how people really argue. Keep this private.
Further study
- Stanford Encyclopedia of Philosophy, Fallacies Read the opening section on what a fallacy is, and note the vocabulary of good and bad reasoning.
- William Lane Craig, Reasonable Faith: Christian Truth and Apologetics Look at how formal arguments are set out in numbered form, and read the objections as carefully as the arguments.
- C. S. Lewis, Mere Christianity Read the opening chapters and notice how Lewis builds an argument in plain prose.
- Thomas Aquinas, Summa Theologiae I, Q. 2: The Existence of God A famous example of an argument set out briefly. Read it slowly and write the premises of one of the ways.
- 1 Peter 3:15 The charter text for giving a reason for hope.
- Acts 17:11 The Bereans test what they hear against Scripture.
- Isaiah 1:18 Come now, and let us reason together.