Butler has it in the line,—
"For discords make the sweetest airs."
Bernardin de St. Pierre, in his Etudes de la Nature:
"C'est des contraires que résulte l'harmonie du monde."
And Burke, in nearly the same words, in his Reflections on the French Revolution:
"You had that action and counteraction, which, in the natural and in the political world, from the reciprocal struggle of discordant powers, draws out the harmony of the universe."
Nor does the sentiment belong exclusively to the moderns. I find it in Horace's twelfth Epistle:
"Nil parvum sapias, et adhuc sublimia cures,
· · · · · ·
Quid velit et possit rerum concordia discors."