Finally there are simple ideas of which no definition can be given; there are also axioms or postulates, or in a word primary principles, which cannot be proved and have no need of proof.
Gottfried Leibniz

For one human being to love another; that is perhaps the most difficult of all our tasks, the ultimate, the last test and proof, the work for which all other work is but preparation.
Rainer Maria Rilke

For those who believe, no proof is necessary. For those who don't believe, no proof is possible.
Stuart Chase

From 1836, down to last year, there is no proof of the Government having any confidence in the duration of peace, or possessing increased security against war.
Richard Cobden

From whichever angle one looks at it, the application of racial theories remains a striking proof of the lowered demands of public opinion upon the purity of critical judgment.
Johan Huizinga

God is a challenge because there is no proof of his existence and therefore the search must continue.
Donald Knuth

God is stronger than their strength, more loving than their uttermost love, and in so far as they have loved and sacrificed themselves for others, they have obtained the infallible proof, that God too lives and loves and gives Himself away.
George A. Smith

He who has laughter on his side has no need of proof.
Theodor Adorno

Here's proof that if you live long enough, anything is possible.
Barry Manilow

I am very abnormal... But it wasn't very long ago that I wasn't so abnormal. I was very normal and headed for a lifetime of paying medical bills as proof of my normalcy.
Dirk Benedict

I don't believe Fermat had a proof. I think he fooled himself into thinking he had a proof.
Andrew Wiles

I mean the word proof not in the sense of the lawyers, who set two half proofs equal to a whole one, but in the sense of a mathematician, where half proof = 0, and it is demanded for proof that every doubt becomes impossible.
Carl Friedrich Gauss

I never believed that Nixon could fully resurrect himself. And the proof of that was in the obits.
Ben Bradlee

I remember the time I was kidnapped and they sent a piece of my finger to my father. He said he wanted more proof.
Rodney Dangerfield

I thought I'd better check this third plate, which is another date, see if there's an image there in the right place that would be consistent with the images on the other plates. That was the final proof.
Clyde Tombaugh

I worked every day there, so I knew all the details. But I needed only some proof. So the proof was photos.
Mordechai Vanunu

I'm proof against that word failure. I've seen behind it. The only failure a man ought to fear is failure of cleaving to the purpose he sees to be best.
George Eliot

If ever we had proof that our nation's pollution laws aren't working, it's reading the list of industrial chemicals in the bodies of babies who have not yet lived outside the womb.
Louise Slaughter

If leaders in the space program had at its beginning in the 1940s, pointed out the benefits to people on earth rather than emphasizing the search for proof of evolution in space, the program would have saved $100 billion in tax money and achieved greater results.
Walter Lang

If you love it, and work really hard at it, it will really happen, I believe. I'm living proof.
Kristen Johnston