Mendacity

Mendacity is not a uniform offence: it changes its colour according to the nature and substance of the offence to which it is rendered or endeavoured to be rendered subservient. Mendacity, employed in drawing down upon an innocent head the destroying sword of justice, is murder: murder, encompassed with all its correspondent terror. Mendacity, employed in the obtainment of money, is but depredation. Yet, while predatory mendacity is punished with death, the punishment for the murderous mendacity is in comparison but a flea-bite.

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[…] Treating the assertion of the witness as the effect, he [Pierre-Simon Laplace] considers as its two possible causes, the veracity or mendacity of the witness on the particular occasion, that is, the truth or falsity of the fact.

Source: wiktionary

Big Daddy: […] Think of all the lies I got to put up with!—Pretenses! Ain't that mendacity? Having to pretend stuff you don't think or feel or have any idea of?

Source: wiktionary

So now the hard Brexiters say, with astonishingly cynical mendacity, that Britain would be better off going it alone.

Source: wiktionary