Meaning
A single decisive check whose result settles a question or reveals a true position. Borrowed from the chemistry test in which litmus dye changes colour to show whether a solution is acid or alkaline, it now means any clear-cut indicator - especially one issue or answer taken as the standard for judging a candidate, plan, or commitment. Journalistic and political register, prone to overuse. Critics object that reducing complex candidates or policies to one litmus test is as crude as the paper itself. Regional use: General English.
Origin
Litmus is a dye extracted from lichens; its name entered English in the early fourteenth century as lit-mose, probably from Old Norse lita, to dye, plus mos, moss, and the Old Norse compound litmosi is attested in a Norwegian law codex of 1316. Wikipedia records that the dye had been used since at least the Viking era and that around 1300 the physician Arnaldus de Villa Nova began using litmus to study acids and bases - blue litmus turns red in acid, red turns blue in alkali. Etymonline dates litmus paper to 1803 and the figurative litmus test to 1957. The metaphor has been strongest in American politics around judicial nominations, and part of its appeal is that the chemical test gives a blunt yes-no answer - general acidity, not exact pH - which is also the standard criticism of the political usage.
Research Sources
References used to check this entry’s meaning, history, or documented forms.
Variants
- a litmus test for something
- a litmus-test issue
- apply a litmus test
Usage Examples
- The committee treated the candidate's answer on housing as a litmus test before agreeing to fund the campaign.
- For many voters, a politician's position on climate policy has become the litmus test of their seriousness.
- How the team handles this outage will be a litmus test of the new manager's leadership under real pressure.