Discerning the Difference

Matthew 7:15 Beware of false prophets, which come to you in sheep's clothing, but inwardly they are ravening wolves.
16Ye shall know them by their fruits. Do men gather grapes of thorns, or figs of thistles?
17Even so every good tree bringeth forth good fruit; but a corrupt tree bringeth forth evil fruit.
18A good tree cannot bring forth evil fruit, neither can a corrupt tree bring forth good fruit.
19Every tree that bringeth not forth good fruit is hewn down, and cast into the fire.
20Wherefore by their fruits ye shall know them.