Without Freedom of Thought, there can be no such Thing as Wisdom; and no such Thing as publick Liberty, without Freedom of Speech.
Men use thought only as authority for their injustice, and employ speech only to conceal their thoughts.
Literature is as old as speech. It grew out of human need for it, and it has not changed except to become more needed.
If you are using dialogue — say it aloud as you write it. Only then will it have the sound of speech.