Formal Fallacies

About the term non sequitur

1. While "the logical argument is a non sequitur" is synonymous with "the logical argument is invalid", the term non sequitur typically refers to those types of invalid arguments which do not constitute formal fallacies covered by particular terms (e.g., affirming the consequent). In other words, in practice, "non sequitur" refers to an unnamed formal fallacy.
2. Non sequitur can simply be a synonym for logical fallacy, be it formal or informal.
3. The Internet Encyclopedia of Philosophy in an article signed by Bradley Dowden defines non sequitur in a more narrower sense as a specific type of fallacy: