Reading passages love arguments: a scientist defends a theory, a critic attacks a book, two historians disagree. To follow them you need words that rate an argument, from rock-solid to falling apart.
Key idea
Strong: cogent (clear and convincing), trenchant (sharp and to the point), valid (logically sound), and three that mean no one can knock it down: irrefutable, incontrovertible, unassailable. Weak: tenuous (thin, slight), flimsy (easily broken), untenable (impossible to defend). And moot: open to debate, or no longer worth debating.
Look inside the long ones. Irrefutable is not able to be refuted; incontrovertible is not able to be turned against (contra + vert); untenable is not able to be held (ten, hold).
The ten words
Common mistake
moot has two senses: open to debate (a moot point) and, in common American use, no longer mattering. In logic, valid describes reasoning that holds, whether or not its premises are true.
| strong | means | weak | means |
|---|---|---|---|
| cogent | clear and convincing | tenuous | thin, slight |
| trenchant | sharp, to the point | flimsy | easily broken |
| irrefutable | can’t be proved wrong | untenable | can’t be defended |
| unassailable | can’t be attacked | moot | debatable, or no longer worth debating |
In logic, valid describes the shape of reasoning, not the truth of the facts. “All cats can fly; Tom is a cat; so Tom can fly” is valid (the conclusion follows) but not true, because the first premise is false. An argument that is valid and has true premises is called sound.