XXVI. (122) And one may here very fitly raise the question for what reason it was that after mentioning the perfection of Noah in virtue, he then immediately adds that "the earth was become corrupt in the sight of God, and was filled with wickedness."31 But perhaps it is not difficult to arrive at a solution of this doubt, for any one who is not exceedingly ignorant of all instruction. (123) We must say therefore, that when an incorruptible species arises in the soul, the mortal part is immediately destroyed; for the birth of virtuous studies is the death of disgraceful ones, since also when light shines forth darkness disappears. On this account, in the law of leprosy, it is most expressly enjoined that "If the living skin arise in the leper, he shall be polluted;"32 (124) and further ratifying this same injunction, and as it were setting a seal to it, he adds, "and the flesh which is sound shall pollute him," delivering this injunction in opposition to what is natural or usual: for all men think the things that are sick the pollution of those that are in health, and those that are dead the pollution of the living, and not, on the contrary, that the healthy and the living are the pollution of the wick and of the dead, but rather, they account them their salvation. (125) But the lawgiver being full of the most modern wisdom in everything, has this peculiarity in his expositions, that he teaches that the healthy and the living are the causes of our not being pure from pollution; for the healthy and living complexion in the soul is truly conviction which rises up against it: (126) when this conviction rises up, it makes a catalogue of all the offences of the soul, and reproaching it with them, and looking sternly at it, it is scarcely able to be stopped in its attacks upon it; and the soul being convicted recognises all its actions by which it has offended against right reason, and perceives that it is foolish, and intemperate, and unjust, and full of pollutions.