I don't think I could pinpoint just one. I have a lot =O
"When I was a boy of 14, my father was so ignorant I could hardly stand to have the old man around. But when I got to be 21, I was astonished at how much the old man had learned in seven years." - Mark Twain
Reporter: What do you think of western civilization?
Mahatma Gandhi: I think it would be a good idea.
"The idea that a believer is happier than a skeptic is no more to the point than the idea that a drunken man is happier than a sober one. The happiness of credulity is a cheap and dangerous quality." - George Bernard Shaw
"Take a close look at nature. Learn your lessons from the sun, moon, and stars. They work so tirelessly, so impersonally. Watch the rivers flow. They have no personal motives. Flowers bloom. They give out a sweet fragrance. There is neither an ego prompting them to do so nor have they selfish desires to fulfill. Similarly, let your work be free from the taint of egoism and selfishness. Follow the path of benevolence of nature. Rise above the idea of the little self or ego. Banish the thought of 'I am doing this.' The more you rise above the little ego the more glorious your work turns out. Such work brings you success, prosperity and peace." - not sure who said it
"...Thomas did not believe the resurrection and, as they say, would not believe without having ocular and manual demonstration himself. So neither will I, and the reason is equally as good for me, and for every other person, as for Thomas." - Thomas Paine
And probably my most favorite, as it changed my philosophy on life almost completely:
Why should I fear death? If I am, death is not. If death is, I am not. Why should I fear that which cannot exist when I do? - Epicurus