Non sequitur

Non sequitur means "does not follow." It is a type of logical fallacy: a bad argument that makes no sense.

It is defined as a deductive argument that is invalid. The argument could have true premises, but still have a false conclusion.

The term "non sequitur" usually refers to those types of invalid arguments which are not named formal fallacies (e.g. post hoc ergo propter hoc). In other words, in practice, "non sequitur" refers to an unnamed formal fallacy.

A non sequitur argument takes something that people accept is true, and says that because this is true, the conclusion is right. The problem is that the conclusion has nothing to do with the premise (original statement that people agree on).

People often have difficulty applying the rules of logic. For example, a person might say this syllogism is valid:

1. All birds have wings.
2. That creature has wings.
3. Therefore, that creature is a bird.

It would only be true if all winged animals were birds (which is not so).