Logical Fallacies

Logic can be a valuable tool for Christians to defend their faith. But mistakes in reasoning can derail even the best argument.

The phrase ad hominem is Latin and means “to the man.” The fallacy is so named because it directs an argument against the person making a claim rather than the claim itself. The critic hopes that people will believe the claim in question is false simply on the basis that there is something objectionable about the person making the claim. For example, “You cannot honestly accept John’s claims about politics because he can’t even find a job!” However, John’s inability to find employment is logically irrelevant to the political claim he is making.

The fallacy comes in two varieties: abusive ad hominem and circumstantial ad hominem. In the abusive ad hominem, the critic attacks his opponent’s character or insults him in an attempt to discredit him in the eyes of the audience. This tactic is common in politics, and it may psychologically sway people. However, it is logically fallacious because a person’s character (or lack thereof) is logically irrelevant to the validity of his argument. Even if the critic’s negative claims about his opponent are true (e.g., he really is a draft-dodger, or he really did spend time in jail), this has no bearing on the position he is advocating.

Name-calling is perhaps the most obvious form of the abusive ad hominem fallacy. When children have a heated disagreement, they sometimes engage in such behavior. As we grow up, we are supposed to become rational and learn to make arguments based on logical reasoning. However, since there is no rationally sound argument for evolution, evolutionists are increasingly resorting to name-calling. I recall a particular instance where an evolutionist launched into a name-calling diatribe against Ken Ham.1 Such immature behavior reminds us that the evolutionary worldview is utterly intellectually bankrupt.2

The circumstantial ad hominem fallacy is when a critic simply dismisses a person’s argument based on the arguer’s circumstances. Suppose Susie makes an argument that taxes on gasoline should be increased. Her opponent, Bobby, tries to refute this by pointing out that Susie’s job is tax-supported, so she is strongly motivated to argue for higher taxes. Bobby concludes that Susie’s argument is wrong since Susie has a bias. Bobby has committed the circumstantial ad hominem fallacy—just because Susie is strongly motivated to defend a particular position does not mean that her argument is faulty.

A non-Christian might argue:

“Christianity isn’t true. You just believe in Christianity because you were brought up in a Christian home. If you were brought up in the Islam religion, you would be a Muslim now.”

This is the circumstantial ad hominem fallacy because the circumstances by which the person became a Christian are not relevant to his or her argument for Christianity. While it may be true that I am much more likely to become a Christian by virtue of being reared in a Christian home, this is utterly irrelevant to whether or not I have a really good logical argument for Christianity. It would be just like saying, “You just believe in the multiplication table because you were taught it in school!” It is true that I probably would not have discovered the multiplication table without someone teaching it to me, but this does not mean that I don’t have some really good reasons to continue to believe in the multiplication table!

An evolutionist might argue:

“Creation isn’t true. You just believe in creation because you read that stuff on the Answers in Genesis website!”

Although the information on the website may have helped people to see the truth of creation and how to argue for it (we hope so!), the person’s argument should be evaluated on its own merit, not on how he arrived at it. The evolutionist is wrong to simply dismiss an argument because he doesn’t like the source.3 The source is not relevant to the argument’s validity.

It may help to note that there is often a difference between a cause and a reason. What is the cause of a person believing in the Christian worldview? Many factors may have contributed: conversations with family, a sermon, prayers of friends, and ultimately the Holy Spirit.4

What is the reason (i.e., the rational justification) for a person believing in the Christian worldview? One really good reason would be that Christianity alone can account laws of logic,5 and science.6 In the above examples, the critic is arbitrarily dismissing a reason for a position on the basis that he does not like the cause of the person coming to that position. But such a dismissal is logically unwarranted and fallacious.

Not all references to a person’s character are necessarily ad hominem fallacies. For example, if a person makes a particular assertion (not an argument, but merely an assertion), and if it can be demonstrated that the person is generally dishonest, it would be perfectly appropriate and relevant to point out that his dishonesty calls into question his credibility on the claim.7 However, even this does not disprove the person’s assertion, since a generally dishonest person will sometimes tell the truth. Moreover, if the person makes an argument, his or her alleged dishonesty is totally irrelevant to the validity of that argument. (An argument is not the same as an assertion.)8 The key is to remember that an argument should be based on its merit, not on the alleged character defects or the circumstances of the person making the argument.

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Footnotes

  1. See Evolving Tactics. Back
  2. Evolution cannot account for rationality, morality, or the success of science, as documented in The Ultimate Proof of Creation. Back
  3. Phrased this way, such a mistake in reasoning is called the genetic fallacy. Back
  4. 1 Corinthians 12:3. Back
  5. See Atheism: An Irrational Worldview. Back
  6. See Evolution: The Anti-science. Back
  7. However, people cannot rationally assert that their opponent is lying on the basis that they disagree on the very claim at issue—that would be begging the question. As an example, consider the evolutionist who says, “Creationists are liars because they teach that the universe is only thousands of years old and that the first life on earth was supernaturally created.” The evolutionist’s assertion is only true if evolution is, but that is the very claim at issue. So, the evolutionist has simply begged the question. Back
  8. An assertion is a proposition, whereas an argument is a chain of propositions where the truth of one is claimed to follow from the others. Logical fallacies concern the “chain of reasoning” between propositions, not the truthfulness of the propositions themselves. See Logical Fallacies: Introduction. Back