"Beloved, do not believe every spirit, but test the spirits to see whether they are from God, because many false prophets have gone out into the world."
1 John 4:1 NASB
We are dealing with eternal matters in this life; often times people don't try to authenticate whether something is true or if it is false.
A lot of people love antiques. When they shop for antiques, they are careful to make sure the piece is indeed the real thing before buying. Shouldn't we be all the more careful when it comes to spiritual (eternal) matters? We should test all things in the light of Scripture.