Lewis returns here to the Law of Nature he discussed in chapter one.
Lewis rarely quotes Scripture in Mere Christianity. However, one passage that would correlate with his statements here can be found in Romans 7:21-24, where the Apostle Paul says, "So I find it to be a law that when I want to do right, evil lies close at hand. For I delight in the law of God, in my inner being, but I see in my members another law waging war against the law of my mind and making me captive to the law of sin that dwells in my members. Wretched man that I am! Who will deliver me from this body of death?" (English Standard Version)