[149] Accordingly, when the greater part of mankind is destroyed in the manners above mentioned, besides an infinity of other ways of less power and importance, it follows of necessity that the arts also must fail, for it cannot be possible to discuss science by itself without some one to reduce it to method and practise. But when those common pestilences relax their fury, and when the human race begins again to recover vigour and to flourish, descending from those who have not been previously destroyed by the evils which pressed upon them, then the arts also begin again to exist, not indeed as they were at first, but in thinner numbers from the diminution of the numbers of those who practise them.