Thought is a kind of opium; it can intoxicate us, while still broad awake; it can make transparent the mountains and everything that exists.
Source: Journal Intime (1882; tr. by Mrs. Humphry Ward, 1892), entry for 3 Feb 1857.
-- Henri Frederic Amiel, (Sep 27 1821-1881), Swiss writer; He is best known for his Journal which is considered a masterpiece of self-analysis.