For men are not only incorruptible in the common species, but also in the proper forms of each individual, which are the rational souls, which cannot be said of other incorruptible things.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic species soul
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

“This rests upon the fact that the guardianship of angels belongs to the execution of Divine providence concerning men. But God's providence acts differently as regards men and as regards other corruptible creatures, for they are related differently to incorruptibility. For men are not only incorruptible in the common species, but also in the proper forms of each individual, which are the rational souls, which cannot be said of other incorruptible things. Now it is manifest that the providence of God is chiefly exercised towards what remains for ever; whereas as regards things which pass away, the providence of God acts so as to order their existence to the things which are perpetual.” source