The speculative intellect can have no pain or sadness on the part of its object, which is truth considered absolutely, and which is its perfection
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic sadness 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

“Grief is then said to be a true passion, by which the soul is troubled, when the passion in the sensitive part causes reason to deflect from the rectitude of its act, so that it then follows the passion, and has no longer free-will with regard to it. In this way passion of the sensitive part did not extend to reason in Christ, but merely subjectively, as was stated above. Reply Obj. 4: The speculative intellect can have no pain or sadness on the part of its object, which is truth considered absolutely, and which is its perfection: nevertheless, both grief and its cause can reach it in the way mentioned above. _______________________ EIGHTH ARTICLE [III, Q. 46, Art. 8] Whether Christ's Entire Soul Enjoyed Blessed Fruition During the Passion?” source