Opinions are not to be learned by rote, like the letters of an alphabet, or the words of a dictionary. They are conclusions to be formed, and formed by each individual in the sacred and free citadel of the mind, and there enshrined beyond the arm of law to reach, or force to shake; ay! and beyond the right of impertinent curiosity to violate, or presumptuous arrogance to threaten.
Lecture VI: Formation of Opinions - A Course of Popular Lectures (1829)