The often used phrase could well be applied to Harriet Beecher Stowe, the author of the novel, "Uncle Tom's Cabin". It was published in 1851-1852 and discussed the injustices and abuses of the institution of slavery in America.
It was a best seller and stirred up significant public sentiment against slavery. In fact, when President Lincoln greeted her he said, "So you're the little lady who started the big war."
It just goes to show the power and potency of ideas. Ideas are important because they ultimately cause people to act one way or another. As the author of Proverbs writes: "As a man thinks in his heart so he is." What we do is dictated by what we believe, whether for good or for bad.