“Secret thoughts are only half free: they fly undisturbed in the skies of the inner freedom, but they can never leave them.”

Source: Call of Duty: My Life Before, During and After the Band of Brothers (2008), p. 107

Address to the court in People v. Lloyd (1920)

"The Holy Dimension", p. 329
Moral Grandeur and Spiritual Audacity: Essays (1997)
Context: It seems as though we have arrived at a point in history, closest to the instincts and remotest from ideals, where the self stands like a wall between God and man. It is the period of a divine eclipse. We sail the seas, we count the stars, we split the atom, but never ask: Is there nothing but a dead universe and our reckless curiosity?
Primitive man's humble ear was alert to the inwardness of the world, while the modern man is presumptuous enough to claim that he has the sole monopoly over soul and spirit, that he is the only thing alive in the universe. … But there is a dawn of wonder and surprise in our souls, when the things that surround us suddenly slip off the triteness with which we have endowed them, and their strangeness opens like a gap between them and our mind, a gap that no words can fill. … What is the incense of self-esteem to him who tastes in all things the flavor of the utterly unknown, the fragrance of what is beyond our senses? There are neither skies nor oceans, neither birds nor trees — there are only signs of what can never be perceived. And all power and beauty are mere straws in the fire of a pure man's vision.

31
Gitanjali http://www.spiritualbee.com/gitanjali-poems-of-tagore/ (1912)

Source: Three Comrades

Original French: Le secret de la liberté est d'éclairer les hommes, comme celui de la tyrannie est de les retenir dans l'ignorance
Source: Oeuvres, Volume 2 http://books.google.com/books?id=iSMVAAAAQAAJ p. 253.

Source: Pretty Little Liars

Variant translation: In a free state, both the tongue and the mind ought to be free.
From Suetonius, The Twelves Caesars, ch. 28