Logical fallacies: appeal to ignorance

There are many logical fallacies, and over the next few weeks and months, I will occasionally focus on a fallacy. While fallacies are typically from the debating sphere and may seem out of place on a blog dedicated to writing, they do appear in writing as well. And not just in social media and blog comments either. They can appear in website and marketing copy, political speeches, opinion pieces, and so on.

Today’s fallacy is appeal to ignorance.

What is the appeal to ignorance fallacy?

An appeal to ignorance fallacy (also known as argumentum ad ignorantiam) is when a speaker uses lack of evidence as proof that a claim is true. This tactic is often used when the speaker recognizes that their opponent has no evidence for their claim, and capitalizes on that evidential absence to support their own position, despite their also not having evidence.

Examples of the appeal to ignorance fallacy

Here are some actual examples of the appeal to ignorance fallacy:

  • You can’t prove God doesn’t exist; therefore, he does.
  • You can’t prove God exists; therefore, he doesn’t.
  • There’s no archaeological evidence of horses existing in the Americas prior to European colonization; therefore, the Book of Mormon is false.
  • There’s no archaeological evidence of horses not existing in the Americas prior to European colonization; therefore, the Book of Mormon is true.

In all the above examples, the speaker assumes that because the opposition’s claim is unproven, then their own claim must be true. However, this fallacy often works both ways. For example, because no proof of God exists, it is neither proof of his existence or non-existence; it is only proof of lack of proof. Neither side can claim lack of proof as evidence for their side.

Using appeal to ignorance is unfair to those you debate, and it’s intellectually lazy for you. Hopefully, these examples explain the importance of focusing on an opponent’s actual claims.

Which logical fallacy should I cover next? Let me know in the comments below.

By Kim Siever

I am a copywriter and copyeditor. I blog on writing and social media tips mostly, but I sometimes throw in my thoughts about running a small business. Follow me on Twitter at @hotpepper.