non sequitur

The term non sequitur is a Latin phrase meaning “it doesn’t follow.” In this error in logic, the writer makes a statement that doesn’t follow logically from the one before it.

False conclusion

A non sequitur may simply be a false conclusion, one that cannot be drawn from the evidence stated:

• Global warming has occurred in the past as a result of natural factors and has never ended in disaster. Therefore, there is no reason to believe that the current global warming is caused by human activity or will create serious problems, and anyone who says it will is merely an alarmist.

Omission of details

Sometimes, however, there is a logical connection that has not been made clear; the writer has left out key steps in the reasoning process because he or she thinks they are obvious.

• John approved the funding before the committee meeting, so we will have to cancel the project.

A logical connection does not exist between these two statements: If the funding was approved, it does not make sense to cancel the project. Of course, with the phrase “before the committee meeting,” the writer is suggesting that something happened at the meeting to reverse the decision. But it is important to state facts clearly rather than simply to imply them. The writer needs to explain what happened between the two events:

• John approved the funding before the committee meeting. But at the meeting, the committee overruled John’s decision, so we will have to cancel the project.