Is "an unbreakable reasoning" idiomatic in English?

(the meaning being that the reasoning has no flaws and can not be invalidated)

Could you propose synonym adjectives of unbreakable in this context that are idiomatic?

Thank you!

  • How can a hypothesis be unbreakable? The purpose of a hypothesis is to discover if it's breakable. If it's unbreakable, then it's a fact, or a theorem or a tautology or similar. Are you rather asking for strongly positive words to describe a hypothesis?
    – gotube
    Commented Dec 4, 2022 at 17:18
  • Recognizing that unbreakable doesn't apply to hypotheses, since they aren't proven yet, and that theorems and postulates are assumed things, what about proofs? For that, the term unassailable, incontestable, or a synonym, might apply. Commented Dec 4, 2022 at 17:46
  • Edited. Just consider the question with "unbreakable reasoning".
    – dragon
    Commented Dec 4, 2022 at 18:05
  • No, it is not idiomatic and sounds like the person speaks another language.
    – Lambie
    Commented Dec 4, 2022 at 18:39

3 Answers 3


For reasoning, the following words might apply: strong, valid, correct, or unassailable:

Wiktionary unassailable
Undeniable, incontestable or incontrovertible.
Synonyms: incontestable, unopposable, impregnable, invulnerable
She won the debate with her unassailable logic.

  • Thank you. So the synonyms from your definition (incontestable, unopposable, impregnable, invulnerable) do not apply to reasoning?
    – dragon
    Commented Dec 4, 2022 at 18:30
  • They do apply. Note the colon after my word unassailable, introducing the Wiktionary definition with additional synonyms. Commented Dec 4, 2022 at 19:08
  • 1
    'Impeccable' is good also. Commented Dec 4, 2022 at 21:23

One word answer(s): indisputable, incontrovertible, self-evident.

Actual answer:

If an argument adheres to the rules of logic without exception, it's said to be logically complete, inferentially true, or logically valid.

Whether or not the premises are true is a separate issue, but if they are, one could say that the argument's ground-truths are valid, or that the premises are confirmed (confirmed analytically or confirmed empirically).

The argument has 'unbreakable reasoning'.
would be synonymous with
The argument has valid ground truths and is logically complete.

  • ground truths? Never heard that....
    – Lambie
    Commented Dec 4, 2022 at 18:36

We often use: unassailable reasoning

: not assailable : not liable to doubt, attack, or question an unassailable argument an unassailable alibi

Merriam Webster

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