To acquire knowledge it is not enough to travel hastily through a
country. Observation demands eyes, and the power of directing them
towards the object we desire to know. There are plenty of people
who learn no more from their travels than from their books, because
they do not know how to think; because in reading their mind is
at least under the guidance of the author, and in their travels
they do not know how to see for themselves.
-- Rousseau, Emile