There is a silence of the tongue, there is a silence of the whole body, there is a silence of the soul, there is a the silence of the mind, and there is the silence of the spirit. The silence of the tongue is merely when it is not incited to angry speech or to stirring up trouble; the silence of the soul is when there are no ugly thoughts bursting forth within it; the silence of the mind is when it is not reflecting on any harmful knowledge or wisdom; the silence of the spirit is when the mind ceases even from stirrings caused by created spiritual beings and all its movements are stirred solely by Being, at the wondrous awe of the silence which surrounds Being. In this state it is truly silent, aware that the silence which is upon it is itself silent.
~ from THE SYRIAC FATHERS ON PRAYER AND THE SPIRITUAL LIFE by Sebastian Brock with gratitude to Fr. Thomas Hopko