Definition

The genetic fallacy arises whenever we dismiss a claim or argument because of its origin or history.

Examples

1) You cannot believe Bob’s idea because it came from his dream.

2) The psychologist says Tim believes in God because Tim lost his father at a young age. So, God doesn’t exist.

3) That is not possible because he got the idea from a science fiction film.

4) Volkswagons are poor cars because the Nazis created them.

Discussion

To better understand the problem, imagine Pythagoras created his theorem after smoking a joint. The drug-induced origin does not make the idea false. Just as we can examine the mathematical proofs for Pythagoras' Theorem and ignore the drug-induced origin, so we can rationally examine the evidence and ignore the origins of any belief.

The genetic fallacy also arises when a person gives evolutionary reasons to explain away beliefs. The problem is explaining the cause for the claim is usually irrelevant to whether the claim is true. For example, let's say there is evidence that belief in the physical world arose for evolutionary reasons. I would be committing the genetic fallacy if I argued the physical world does not exist because it arose for evolutionary reasons. The evolutionary explanation is only helpful in such debates if I already have strong and independent arguments against belief in the physical world.

So, the genetic fallacy often arises when people confuse reasons with causes. To understand the difference, notice that the cause of your deducing “all As are Cs” from “all As are B's” and “all Bs are Cs” is brain activity. Let's say the cause of this operation is "Q Fibers firing" in the brain.

However, your reasons for believing “all As are Cs” are the two premises and their logical relation (i.e. “all As are Bs” and “all Bs are Cs” implies “all As are Cs”). It is important not to confuse reasons and causes because the neuroscientific causes of my deduction are irrelevant to the logical operations of my deduction. The relationship between reasons and causes is complex, but the point is that we do not usually prove or disprove a belief by identifying its cause. To think otherwise is to commit the genetic fallacy.

How to avoid

Focus on the arguments, not on the origin or history of the arguments. Remember that a bad source does not make an argument bad. Only false premises or a faulty inference make an argument bad.

Exercise

  1. Are the following genetic fallacies?
  • Volkswagon Beetles are poor cars because they were created by Nazis.
  • Kekule has an interesting theory about the ring structure of Benzene, but it cannot be true because he got the idea from a dream.
  • “Your honor, we cannot trust Bob’s testimony because several psychiatrists have diagnosed him as a pathological liar, and records show he lied under oath in several other cases.”
  1. Why do people fall for this fallacy?

Answers

  1. The first two are genetic fallacies; the third is not fallacious.
  2. This fallacy arises because even intelligent people confuse a) reasons and causes, b) psychological and logical explanations, and C) sources and arguments.

Return to Logic Home Page      Go to Next Fallacy in Chapter 3      Go to Chapter 4      Take a Quiz