But when erring reason proposes something as being commanded by God, then to scorn the dictate of reason is to scorn the commandment of God.

Thomas Aquinas (1225–1274) Italian friar, philosopher, theologian

Summa Theologica 1a-2ae, q. 19, art. 5, ad 2 (1265-1274)
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Often quoted without the first clause, which changes the meaning. Alt. trans.: "To disparage the dictate of reason is equivalent to contemning the command of God."