That the inferior are subject to the superior, is not for the benefit of the superior, but rather to their detriment; because since to do evil belongs in a pre-eminent degree to unhappiness, it follows that to preside in evil is to be more unhappy.
 Thomas Aquinas, Summa Theologica (1274). copy citation

add
Author Thomas Aquinas
Source Summa Theologica
Topic unhappiness evil
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

“For it belongs to wicked men to be joined to and subject to those whom they see to be stronger, in order to carry out their own wickedness. Reply Obj. 3: The demons are not equal in nature; and so among them there exists a natural precedence; which is not the case with men, who are naturally equal. That the inferior are subject to the superior, is not for the benefit of the superior, but rather to their detriment; because since to do evil belongs in a pre-eminent degree to unhappiness, it follows that to preside in evil is to be more unhappy. _______________________ THIRD ARTICLE [I, Q. 109, Art. 3] Whether There Is Enlightenment in the Demons? Objection 1: It would seem that enlightenment is in the demons. For enlightenment means the manifestation of the truth.” source