No one believes a liar even when he tells the truth

Liars ... when they speak the truth they are not believed.

The Liar’s punishment is not in the least that he is not believed, but that he cannot believe anyone else.

The Liar’s punishment is not in the least that he is not believed, but that he cannot believe anyone else. — George Bernard Shaw

The liar is a person who uses the valid designations, the words, in order to make something which is unreal appear to be real. He says, for example, "I am rich," when the proper designation for his condition would be "poor." He misuses fixed conventions by means of arbitrary substitutions or even reversals of names. If he does this in a selfish and moreover harmful manner, society will cease to trust him and will thereby exclude him. What men avoid by excluding the liar is not so much being defrauded as it is being harmed by means of fraud. Thus, even at this stage, what they hate is basically not deception itself, but rather the unpleasant, hated consequences of certain sorts of deception. It is in a similarly restricted sense that man now wants nothing but truth: he desires the pleasant, life-preserving consequences of truth. He is indifferent toward pure knowledge which has no consequences; toward those truths which are possibly harmful and destructive he is even hostilely inclined.

A man who lies to himself is the worst liar of all.

He who does not lie does not know what truth is.

Whoever has even once become notorious by base fraud, even if he speaks the truth, gains no belief.

Friendship is impossible with a liar.

2084. He that does not speak Truth to me, does not believe me when I speak Truth.

There is no liar like the one who lies to himself. He has a fool indeed for an audience.

A lie cannot live.

The liar wants to be believed, but lying undermines the foundation for credibility.

The only thing worse than a liar is a liar that's also a hypocrite!