Cogency
Cogency is the ampliative analogue of Soundness. An Ampliative Argument is cogent when:
- The premises are all true, AND
- The inferential link is strong: the premises make the conclusion sufficiently probable
Why not just soundness?
Strength comes in degrees (unlike Validity, which is binary). A cogent argument doesn’t guarantee its conclusion; it raises Credence in it.
| Deductive | Ampliative | |
|---|---|---|
| Good link | Valid | Strong |
| Good link + true premises | Sound | Cogent |
Most real-world reasoning (science, courts of law, medical diagnosis, everyday belief) is ampliative. We almost never have deductive proofs, so the standard we hold these arguments to is cogency, not soundness.
Two ways to attack a cogent-looking argument
- Show a premise is false
- Show the inferential link isn’t actually strong (e.g., biased sample, weak analogy, an alternative explanation fits the data better)