John Chrysostom

"Yea verily, and I have counted all things but loss." Why, he means, do I say this of the Law? Is not the world good? Is not the present life good? but if they draw me away from Christ, I count these things loss. Why? "for the excellency of the knowledge of Jesus Christ my Lord." For when the sun hath appeared, it is loss to sit by a candle: so that the loss comes by comparison, by the superiority of the other. …

Homily on Philippians 11 ↗

Ambrose of Milan

And the Apostle teaches us how to dung it, saying: "I count all things but dung, that I may gain Christ," and he, through evil report and good report, attained to pleasing Christ. For he had read that Abraham, when confessing himself to be but dust and ashes, in his deep humility found favour with God. He had read how Job, sitting among the ashes, regained all that he had lost. He had heard in the utterance of David, how God "raiseth the poor out of the dust, and lifteth the needy out of the dunghill."

Concerning Repentance, Book 2 ↗

Thomas Aquinas

He explains this: first, that he acted thus in order to know Christ, and secondly to obtain Him. In regard to the first he says, Indeed I count everything as loss. This is true, if he had continued to depend on them. What I did formerly, I now regard a loss on account of my desire for a correct understanding of Christ, my Lord: "For I decided to know nothing among you except Jesus Christ and him crucified" (1 Cor. 2:2). Because of the surpassing worth of knowing Christ Jesus my Lord, since this transcends all knowledge. …

Commentary on Philippians ↗