To Florus 4.116

Either both are denied together or both are accepted together. Although one can reject both, one cannot choose only one. It is, however, easier for an unlawful union to be burdened with the fault of will while the fruitfulness of its seeds remains defended, than for the sexual act to be vindicated while its fruits are accused. Your wavering between fear and impiety will therefore not establish new rules of argument, allowing you to accept one of two connected things and exclude what belongs to it. “Light-footed deer will graze in the sky” (Virgil, Eclogues 1.59) before a conclusion can be denied after its premise has settled the matter.

The apostle Paul uses this form of argument when he says, “If the dead do not rise, neither has Christ risen. If Christ has not risen, your faith is empty” (1 Corinthians 15:16–17). But now Christ has risen; therefore it is certain that a day of resurrection awaits the dead (compare 1 Corinthians 15:20–23). To press this same point upon the reader with a shorter example: suppose there is doubt whether what is just is good. I ask whether you acknowledge that everything just is honorable. Once that is granted, I add another question: do you also pronounce everything honorable good? Once that too is granted, whether you like it or not, I conclude: if everything just is honorable, and everything honorable is good, then everything just is good. Anyone who tries to resist this conclusion after accepting the first premises does not shake reason’s structure but exposes himself to ridicule.

To bring the comparison back to the case: the question is whether sin exists in nature. I asked whether you would concede that no sin exists without will. You agreed, as your own words testify. I added whether you thought an infant possessed will. You denied this too. What follows as the third point, if sin does not exist without will? This is so certain that it cannot be doubted even by the Academics, whose wealth consists in holding nothing certain. So when you deny the third point after the first two premises, although it contains their conclusion, you do not overturn the foundations of reason: you reveal your frenzy.