Non Sequitur
A logical fallacy where the conclusion does not follow from the premises; the evidence or reason presented is irrelevant or adds very little support to the conclusion.
THE IDEA
Non Sequitur
(also known as: derailment, “that does not follow”, irrelevant reason, invalid inference, non-support, argument by scenario [form of], false premise [form of], questionable premise [form of])
Description: When the conclusion does not follow from the premises. In more informal reasoning, it can be when what is presented as evidence or reason is irrelevant or adds very little support to the conclusion.
Logical Form:
- Premise 1: [statement]
- Premise 2: [statement]
- Conclusion: [statement that does not follow from premises]
Example #1:
- Premise 1: People generally like to walk on sand.
- Premise 2: Sand is a natural material.
- Conclusion: Therefore, we should have sand floors in our homes.
Explanation: As cool as the idea of sand floors might sound, the conclusion does not follow from the premises. The fact that people generally like to walk on sand does not mean that they want sand in their homes, just like because people generally like to swim, they shouldn’t flood their houses.
Example #2:
- Premise 1: Phil makes the best burgers in town.
- Premise 2: Phil is a good cook.
- Conclusion: Therefore, Phil would make a great President of the United States.
Explanation: I bet Phil makes one heck of a burger, but it does not follow that he should be President.
Exception: There are no exceptions to this rule. Any good argument must have a conclusion that follows from the premises.
Tip: One of the best ways to expose non sequiturs is by constructing a valid analogy that exposes the absurdity in the argument.
Variations: There are many forms of non sequiturs including argument by scenario, where an irrelevant scenario is given in attempt to support the conclusion. Other forms use different rhetorical devices that are irrelevant to the conclusion. A false or questionable premise is a separate problem: an argument can have a valid inference even when a premise is false. Ask both whether the premises are justified and whether the conclusion follows from them.
When to use it
In debates, point out when an opponent's conclusion is not supported by their evidence to highlight a flawed argument.
In scientific research, ensure that the data and analysis actually support the claimed conclusion, avoiding leaps in logic.
In legal reasoning, verify that the verdict or judgment follows from the evidence presented, not from emotional appeals or irrelevant facts.
In everyday decision-making, avoid jumping to conclusions that are not logically connected to the information at hand, such as assuming a correlation implies causation.
FROM THEORY TO EVERYDAY LIFE
In practice
Example #1: Sand Floors
Premises: People generally like to walk on sand. Sand is a natural material. Conclusion: Therefore, we should have sand floors in our homes. This is a non sequitur because liking to walk on sand does not imply wanting sand indoors, just as liking swimming does not imply flooding a house.
Example #2: Phil for President
Premises: Phil makes the best burgers in town. Phil is a good cook. Conclusion: Therefore, Phil would make a great President. This is a non sequitur because cooking skill does not logically lead to presidential competence.
A MOMENT TO REFLECT
Put it to work.
Think of an argument you recently heard or made where the conclusion did not follow from the premises. How could it be restructured to be valid?
Why is it important to ensure that conclusions logically follow from premises in both formal and informal reasoning?
Can you identify a non sequitur in a political speech, advertisement, or everyday conversation? What made the conclusion irrelevant to the evidence?
CONTINUE THE CONVERSATION
Source texts
- Logically Fallacious - The Ultimate Collection of Over 300 Logical Fallacies