Personality pertains of necessity to the dignity of a thing, and to its perfection so far as it pertains to the dignity and perfection of that thing to exist by itself (which is understood by the word "person") . Now it is a greater dignity to exist in something nobler than oneself than to exist by oneself.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic personality perfection
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/19950/pg19950-images.html

Context

“And because human nature is united to the Word, so that the Word subsists in it, and not so that His Nature receives therefrom any addition or change, it follows that the union of human nature to the Word of God took place in the person, and not in the nature. Reply Obj. 2: Personality pertains of necessity to the dignity of a thing, and to its perfection so far as it pertains to the dignity and perfection of that thing to exist by itself (which is understood by the word "person") . Now it is a greater dignity to exist in something nobler than oneself than to exist by oneself. Hence the human nature of Christ has a greater dignity than ours, from this very fact that in us, being existent by itself, it has its own personality, but in Christ it exists in the Person of the Word.” source