12 What does he mean by this? As I take it, that goodness can with difficulty gain a hold upon human nature, like fire upon green wood; while most men are ready and disposed to join in evil, like stubble, I mean, ready for a spark and a wind, which is easily kindled and consumed from its dryness. For more quickly would any one take part in evil with slight inducement to its full extent, than in good which is fully set before him to a slight degree. For indeed a little wormwood most quickly imparts its bitterness to honey; while not even double the quantity of honey can impart its sweetness to wormwood: and the withdrawal of a small pebble would draw headlong a whole river, though it would be difficult for the strongest dam to restrain or stay its course.
Source: Orations (New Advent)