to swear blind

1 8.4

Say very firmly that something is true, even if others doubt it

phrasal verb

: jurar ciegamente

They swore blind that they would arrive on time, but they were late.

Examples

I'll come, but only if you two swear blind you will not leave me on my own with him.

Last Chance Harvey (2008)
She swore blind that the dolphins talked to her when they saved us from drowning.

Fiction book (1991)
I worked with a man like that once, swore blind he was my best mate.

The Purging Hour (2015)
That I have fought with myself over that night, one half of me swearing blind that I tied a simple slipknot, the other half convinced that I tied the Langford double.

The Prestige (2006)
He swore blind that he had never seen the document before.
Despite the evidence against him, she swore blind that he was innocent.

Synonyms

to swear

vsto swear blind

Formal

∞ 4.6

To make a serious promise, often in court

insists very firmly that something is true despite others doubt

Antonyms

to doubt

∞ 1.3

To feel not sure about something or think it is not true

How Certain

to swear blind

1 8.4

to insist

∞ 2.8

to assert

229 3.9

claim

818 3.3

guess

768 1.0

Surface Forms

swear blind infinitive

swearing blind present participle

swears blind third person singular

swore blind past

sworn blind past participle

Morphology

swear + blind

There is a visible link between 'swear' (to assert solemnly) and 'blind' used as an intensifier, so learners who know both words may suspect the phrase means to assert very strongly. However, the specific sense 'insist something is true despite doubt' is a metaphorical, conventionalized usage that is not fully predictable from the parts, so it is only partially transparent to a B1 learner.

Etymology

Swear blind may come from a strong image: someone saying 'I swear' and adding they would go blind if they were lying. So, when someone swears blind, they insist very firmly that something is 'true', even if others doubt them.