Faith is not seen in the heart wherein it abides, as the soul of a man may be seen by another from the movement of the body
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic faith heart
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/17611/pg17611-images.html

Context

“Whether Our Intellect Knows the Habits of the Soul by Their Essence? Objection 1: It would seem that our intellect knows the habits of the soul by their essence. For Augustine says (De Trin. xiii, 1) : "Faith is not seen in the heart wherein it abides, as the soul of a man may be seen by another from the movement of the body; but we know most certainly that it is there, and conscience proclaims its existence"; and the same principle applies to the other habits of the soul. Therefore the habits of the soul are not known by their acts, but by themselves.” source