The argument from incredulity occurs if someone refuses to accept an argument simply because he cannot personally understand it. Flat-Earthers very frequently use this logical fallacy.
The general form of the fallacy:
- Premise 1: I cannot understand how X can happen
- Premise 2 (unstated): If X happens, I can understand how it could happen
- Conclusion: X is false.
The fallacy happens in the second, unstated premise. If the subject cannot understand the fact X, it does not mean the fact is wrong, or that nobody else can understand it.
Usually, this fallacy is apparent in how they answer a statement they cannot understand; for example, by using emotional exclamations that do not address the topic.
Sometimes, the fallacy occurs not because the subject cannot understand, but because they knowingly refuse to understand. It can usually happen because of emotional indoctrination. When people become emotionally attached to a particular belief, they would no longer be able to use their reasoning skills, especially when confronted with the facts that go against their worldview.