For the heart is the principle of the senses; and from the organ of generation proceeds the seminal virtue, which is virtually the entire animal. Consequently they have their proper movements naturally: because principles must needs be natural, as stated above (Reply Obj.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic virtue heart
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/17897/pg17897-images.html

Context

“But they are not moved at the command of the reason or intellect, because these movements are conditioned by a certain natural change of heat and cold, which change is not subject to the command of reason. This is the case with these two organs in particular, because each is as it were a separate animal being, in so far as it is a principle of life; and the principle is virtually the whole. For the heart is the principle of the senses; and from the organ of generation proceeds the seminal virtue, which is virtually the entire animal. Consequently they have their proper movements naturally: because principles must needs be natural, as stated above (Reply Obj. 2). ________________________
QUESTION 18 OF THE GOOD AND EVIL OF HUMAN ACTS, IN GENERAL (In Eleven Articles)
We must now consider the good and evil of human acts. First, how a human act is good or evil; secondly, what results from the good or evil of a human act, as merit or demerit, sin and guilt.
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