The essence of all slavery ...

The essence of all slavery consists in taking the product of another\'s labor by force. It is immaterial whether this force be founded upon ownership of the slave or ownership of the money that he must get to live.
The essence of all slavery consists in taking the product of another's labor by force. It is immaterial whether this force be founded upon ownership of the slave or ownership of the money that he must get to live.

More phrases

All the great things are simple, and many can be expressed in a single word: freedom, justice, honor, duty, mercy, hope.
I know but one freedom and that is the freedom of the mind.
 Antoine de Saint-Exupéry
Freedom is not worth having if it does not connote freedom to err.
The amount of happiness that you have depends on the amount of freedom you have in your heart.
 Thích Nhất Hạnh
Without freedom of thought, there can be no such thing as wisdom - and no such thing as public liberty without freedom of speech.

Quotes from the same author

Everyone thinks of changing the world, but no one thinks of changing himself.
We lost because we told ourselves we lost.
The two most powerful warriors are patience and time.
The strongest of all warriors are these two — Time and Patience.
The life of our class, of the wealthy and the learned, was not only repulsive to me but had lost all meaning. The sum of our action and thinking, of our science and art, all of it struck me as the overindulgences of a spoiled child.