Truth

It is a truth universally acknowledged, that a single man in posession of a good fortune must be in want of a wife.
However little known the feelings or views of such a man may be on his first entering a neighborhood, this truth is so well fixed in the minds of the surrounding families, that he is considered as the rightful property of someone or other of their daughters.

No real gentleman will tell the naked truth in the presence of ladies.
Mark Twain

The problem with truth, as a word or concept, is that it has several meanings (it is polysemous), and these senses are often contradictory. This situation is complicated by the fact that it involves feelings, as in its opposition to »lies«, while falsity can be demonstrated. Another problem arises when truth is equated with reality, since reality is subject to perception, thus mostly variable according to individuals. When truth is invoked in the case of a fact, it can be proven or disproven. The logician's truth is of little use, since it evacuates contents. But one point needs to be stressed: truth, as the Old Pirate said a year ago, is not a matter of belief. The test would be simple if the meaning of the verb »to believe« did not interfere with the meaning of the verb »to think«. One should also be careful not to confuse »I believe X« (X being a statement) and »I believe in Y« (Y = a concept). You cannot have an opinion on the fact that a tugboat is a boat. Last but not least: the act of believing does not make something exist.

If a thousand old beliefs were ruined in our march to truth we must still march on.

(Stopford Brooke)

Truth is absolute. The fact that everyone once believed that the world is flat didn't succeed in unrounding it by a single millimeter. If five billion people are making a mistake, it's still a mistake.

Seek the truth – or the truth will seek you!

Truth is never pure, and rarely simple.

Oscar Wilde--The Importance of Being Earnest Act i

When you want to fool the world, tell the truth.
Bismarck

One of the best things about telling the truth is that
you don't have to remember what you said.

(A good liar needs an excellent memory)

The pure and simple truth is rarely pure and never simple.
Oscar Wilde

To a man of a mathematical turn of mind – to a student and lover of the exact sciences these inaccuracies of expression – this inability to understand exactly how things are must be a constant source of annoyance; and to one who, like myself, writes this turn of mind to an ardent love of truth, for its own sake – the reflection that the English language does not enable us to speak the truth with exactness (hello, mr. president!), is peculiarly painful.
John Phoenix, A New System of English Grammar, 1854.

It is hard to believe that someone is telling the truth when you are quite sure that if you were in his place you would lie.