Believe it or not, Christians are to think critically. Now before you drag me off and stone me, let me remind you that there are at least two different meanings of the word “critical”. One has to do with negative criticising and condemning. That is not what I have in mind here.
The other meaning has to do with careful evaluation, testing, discerning, assessing, and judging. That is something Christians should do all the time, as Scripture makes clear:
-Proverbs 14:33 Wisdom reposes in the heart of the discerning
-Isaiah 1:18 “Come now, let us reason together,” says the LORD.
-1 Corinthians 2:15 The spiritual man makes judgments about all things
-1 Thessalonians 5:21-22 Test everything.
An important part of critical thinking is the use of logic. This is not the place to say much more about logical thinking in general, and the basic principles of logic. Instead I here want to just focus on what are known as logical fallacies. Simply stated, these come in two varieties: formal fallacies, which have to do with errors in the way an argument is put together; and informal fallacies, which have to do with errors in clarity or soundness of the reasoning process.
As to the former, let me only very briefly discuss these. Referred to as deductive reasoning, they have to do with a logical formulation, or a syllogism. Here are some basic features of a syllogism:
-A syllogism is an argument with two (or more) premises and a conclusion.
-An argument is valid when the conclusion necessarily follows from the premises. In such an argument it is logically impossible for the premises to be true and the conclusion false.
-An argument is invalid if the premises do not entail the conclusion.
-An argument is sound if it is both valid and the premises are true.
This is a sound argument:
1. All men are mortal (major premise)
2. Socrates is a man (minor premise)
3. Therefore, Socrates is mortal (conclusion)
This is an invalid argument (the conclusion does not follow from the premises):
1. All men are from Mars
2. All women are from Mars
3. Therefore, all men are women
This is a valid argument, but not sound, because a premise is not true:
1. All men are from Mars
2. Bill is a man
3. Therefore, Bill is from Mars
This argument is valid, but not necessarily sound:
1. God created all things
2. Evil exists
3. God created evil
e.g., Christians could qualify premise 1: evil is not a thing or substance, but a privation.
Informal fallacies
But for the rest of this article I want to concentrate on common informal fallacies, or mistakes in the reasoning process. There are quite a few such fallacies, but here I offer a dozen of the more common forms:
Non sequitur (Latin, “it does not follow”). An argument is a non sequitur if the conclusion does not follow from the premise. In it the conclusion can be either true or false, but the argument is a fallacy because the conclusion does not follow from the premise.
Example: The early Christians were pacifists because they did not intervene when Paul was arrested.
Attacking the person (ad hominem). An attack on the person making an argument, instead of responding to the argument itself.
Examples:
“You are just a religious bigot.”
“You are homophobic.”
“Bill, you do realise that your obsession with homosexuality raises serious questions about your own sexuality.”
Begging the question (petitio principii). A type of fallacy occurring when the proposition to be proved is assumed implicitly or explicitly in one of the premises. The conclusion is snuck into the premises. It is a circular argument. It assumes what it is trying to prove.
Example: “Only an untrustworthy person would run for office. The fact that politicians are untrustworthy is proof of this.”
Category mistake. This involves comparing apples with oranges. It mixes two ideas that don’t belong together.
Example: “Just as South Africa had apartheid, so you will not allow same-sex marriage.” But skin colour or race is an innate characteristic, while sexual preference is not.
Red herring. Changing the subject to some irrelevant or different issue.
Example: You might be debating the issue of abortion, and someone throws in another issue, such as capital punishment, which is really a separate issue.
False dilemma. This involves a situation in which two alternative points of view are held to be the only options, when in reality there exists one or more other options which have not been considered.
Example: Either you support heroin injecting rooms or you want addicts to die. But in fact there is a third option. Because you love the heroin addict, and want him to live, you will seek to get him free of his heroin addiction. Getting the addict off drugs is the loving thing to do.
A straw man argument. This is a logical fallacy based on misrepresentation of an opponent’s position. You present a misrepresentation or distortion of the opponent’s position, making it easier to refute.
Example: Christians want to set up a theocracy and force people to become Christians.
The Naturalistic Fallacy. Confusing ‘is’ with ‘ought,’ or turning description into prescription.
Example:
Everyone is doing it (eg., premarital sex). Therefore, there is nothing wrong with premarital sex. So is genocide and mass murder OK because nature has floods and tsunamis?
Simple ambiguity, or equivocation. A word or phrase is used in two different senses, or with two or more meanings.
Example
1. All sides of rivers are banks.
2. All banks have money.
Therefore,
3. All sides of rivers have money.
It is always important that we clearly define our terms in a given argument, and make sure the other side knows and accepts our meanings of the terms.
Appeal to pity (argumentum ad misericordiam). An emotional appeal that overlooks the facts of a case.
Example: “We should allow embryonic stem cell research so that Christopher Reeve can walk again.” This is not making an argument, it is appealing to our emotions.
Appeal to authority. There is a place for authority, but often it is a misplaced appeal.
Examples:
“Santa Claus exists because my dad says so.”
“There is no God because Dawkins said so.”
Genetic fallacy. Confusing the origins of an idea with reasons for believing in an idea. An argument is rejected or regarded as mistaken or false because it comes from a bad or questionable source.
Examples:
“You were born in Christian America, and that is why you are a Christian.” But this is irrelevant to the argument. The issue is, are there good grounds for believing in Christianity?
“You are against abortion because you are a Catholic.” Whether or not one is a Catholic is beside the point. Are there good reasons for holding that abortion is wrong?
These then are some of the more common logical fallacies. We need to be aware of these, and train our minds to spot them. Believers need to be able to think clearly, critically and logically, both as they assess other people’s arguments, and as they make their own.
Update: For further reading
There are plenty of textbooks on logic, logical fallacies, and critical thinking. Both Christians and non-Christians can benefit from them. But here are five books penned by Christians discussing the same sorts of issues. Some of the volumes cover much more than basic logic, such as Jacobs and Poythress.
T. Ryan Byerly, Introducing Logic and Critical Thinking. Baker 2017.
Norman Geisler and Ronald Brooks, Come, Let Us Reason: An Introduction to Logical Thinking. Baker, 1990.
Alan Jacobs, How to Think. Profile Books, 2017.
Vern Poythress, Logic: A God-Centered Approach to the Foundation of Western Thought. Crossway, 2013.
Douglas Wilson and N. D. Wilson, The Amazing Dr. Ransom’s Bestiary of Adorable Fallacies. Canon Press, 2017.
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