If we can't think for ourselves, if we're unwilling to question authority, then we're just putty in the hands of those in power. But if the citizens are educated and form their own opinions, then those in power work for us. In every country, we should be teaching our children the scientific method and the reasons for a Bill of Rights. With it comes a certain decency, humility and community spirit. In the demon-haunted world that we inhabit by virtue of being human, this may be all that stands between us and the enveloping darkness.
-- Carl Sagan, The Demon-Haunted World
You can't convince a believer of anything; for their belief is not based on evidence, it's based on a deep seated need to believe.
-- Carl Sagan (attributed: source unknown)
Aritosthenese's only tools were sticks, eyes, feet, and brains; plus a zest for experiment. With those tools he correctly deduced the circumference of the Earth, to high precision, with an error of only a few percent. That's pretty good figuring for 2200 years ago.
-- Carl Sagan, Cosmos television series, quoted from The Carl Sagan Electronic Monument
http://www.youtube.com/v/R7n71pm0K04">The beautiful intro to the Cosmos television series. Carl Sagan talks about the universe and our place within it. (5 minutes)