I like this quote in particular as so many people are distrustful of science and rationality in spite of the thousands of benefit's they experience as a result every day.
We have already compared the benefits of theology and science. When the theologian governed the world, it was covered with huts and hovels for the many, palaces and cathedrals for the few. To nearly all the children of men, reading and writing were unknown arts. The poor were clad in rags and skins -- they devoured crusts, and gnawed bones. The day of Science dawned, and the luxuries of a century ago are the necessities of to-day. Men in the middle ranks of life have more of the conveniences and elegancies than the princes and kings of the theological times. But above and over all this, is the development of mind. There is more of value in the brain of an average man of to-day -- of a master-mechanic, of a chemist, of a naturalist, of an inventor, than there was in the brain of the world four hundred years ago.
These blessings did not fall from the skies. These benefits did not drop from the outstretched hands of priests. They were not found in cathedrals or behind altars -- neither were they searched for with holy candles. They were not discovered by the closed eyes of prayer, nor did they come in answer to superstitious supplication. They are the children of freedom, the gifts of reason, observation and experience -- and for them all, man is indebted to man.
-- Robert Green Ingersoll, "God In The Constitution"
God in the Constitution
Also, the man had a sense of humour;
The old lady who said there must be a devil, else how could they make pictures that looked exactly like him, reasoned like a trained theologian -- like a doctor of divinity.
-- Robert Green Ingersoll, from "Superstition" (1898)
The doctrine that future happiness depends upon belief is monstrous. It is the infamy of infamies. The notion that faith in Christ is to be rewarded by an eternity of bliss, while a dependence upon reason, observation and experience merits everlasting pain, is too absurd for refutation, and can be relieved only by that unhappy mixture of insanity and ignorance, called "faith." What man, who ever thinks, can believe that blood can appease God? And yet, our entire system of religion is based upon that belief. The Jews pacified Jehovah with the blood of animals, and according to the Christian system, the blood of Jesus softened the heart of God a little, and rendered possible the salvation of a fortunate few. It is hard to conceive how the human mind can give assent to such terrible ideas, or how any sane man can read the Bible and still believe in the doctrine of inspiration.
-- Robert Green Ingersoll, The Gods