Know them.

¹⁵  "Be on your guard against false prophets; they come to you looking like sheep on the outside, but on the inside they are really like wild wolves. ¹⁶  You will know them by what they do. Thorn bushes do not bear grapes, and briers do not bear figs. ¹⁷  A healthy tree bears good fruit, but a poor tree bears bad fruit. ¹⁸  A healthy tree cannot bear bad fruit, and a poor tree cannot bear good fruit. ¹⁹  And any tree that does not bear good fruit is cut down and thrown in the fire. ²⁰  So then, you will know the false prophets by what they do." Matthew 7:15-20 (TEV)