The words “peace, calm, quiet, silence” have each their own shade of meaning, but it is not easy to define them.
Quiet is a condition in which there is no restlessness or disturbance.
Calm is a still unmoved condition which no disturbance can affect—it is a less negative condition than quiet.
Peace is a still more positive condition; it carries with it a sense of settled and harmonious rest and deliverance.
Silence is a state in which either there is no movement of the mind or vital or else a great stillness which no surface movement can pierce or alter.
Sri Aurobindo – Letters on Yoga – II: CWSA,Vol. 29, p. 137
Do not confuse calm with inertia. Calm is self-possessed strength, quiet and conscious energy, mastery of the impulses, control over the unconscious reflexes. In work calm is the source of efficiency and an indispensable condition for perfection.
The Mother – Words of the Mother – II: CWM, Vol. 14, p.134
Calm are the thoughts, the words and the acts of one who has liberated himself by the true knowledge and has achieved a perfect tranquility.
The Mother – Questions and Answers: CWM,Vol. 3, p. 223
The sage who has steeped himself in the Teaching, becomes perfectly peaceful like a deep lake, calm and clear.
The Mother – Questions and Answers: CWM,Vol. 3, p. 219
Then a calm Power seated above our brows
Is seen, unshaken by our thoughts and deeds,
Its stillness bears the voices of the world:
Immobile, it moves Nature, looks on life.
Sri Aurobindo – Savitri: CWSA, Vol. 34 , Book Nine, p. 571