Works before faith are sins; the philosophers' virtues were vices
In chapter 1 of the next book he sets out to prove, expressly and specifically, following Augustine and the truth itself, that all works done before faith, from which the Christian religion begins, are nothing but sins, and that moral goodness is ascribed to them falsely and in error.
And, as follows from this, in chapter 8 he shows that the virtues of the philosophers were not true virtues but vices.
Latin
XXXV. Capite vero primo libri sequentis ex professo & speciatim probare aggreditur, juxta Augustinum & veritatem ipsam, omnia opera facta ante fidem, a qua religio Christiana incipit, non aliud quam peccata esse, & falso ac per errorem ipsis tribui bonitatem moralem. Et quod inde consequens est, capite octavo ostendit Philosophorum virtutes non fuisse veras virtutes, sed vitia.