But erring reason sometimes proposes what is against the command of a higher power, namely, God Whose power is supreme. Therefore the decision of an erring reason does not bind. Consequently the will is not evil if it be at variance with erring reason.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic evil power
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

“2: Further, according to Augustine, the command of a lower authority does not bind if it be contrary to the command of a higher authority: for instance, if a provincial governor command something that is forbidden by the emperor. But erring reason sometimes proposes what is against the command of a higher power, namely, God Whose power is supreme. Therefore the decision of an erring reason does not bind. Consequently the will is not evil if it be at variance with erring reason. Obj. 3: Further, every evil will is reducible to some species of malice. But the will that is at variance with erring reason is not reducible to some species of malice. For instance, if a man's reason err in telling him to commit fornication, his will in not willing to do so, cannot be reduced to any species of malice.” source