These verses will make it clear:
John 8:32 (NASB)
32 and you shall know the truth, and the truth shall make you free."
1 Thessalonians 5:20-21(NASB)
20 do not despise prophetic utterances.
21 But examine everything carefully; hold fast to that which is good;
1 John 4:1(NASB)
1 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.
Now these were more noble-minded than those in Thessalonica, for they received the word with great eagerness, examining the Scriptures daily, to see whether these things were so.
1 Timothy 4:11(NASB)
11 "Prescribe and teach these things."
18 For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who suppress the truth in unrighteousness,
32 and, although they know the ordinance of God, that those who practice such things are worthy of death, they not only do the same, but also give hearty approval to those who practice them.
1 Timothy 4:1-3(NASB)
1 But the Spirit explicitly says that in later times some will fall away from the faith, paying attention to deceitful spirits and doctrines of demons,
2 by means of the hypocrisy of liars seared in their own conscience as with a branding iron,
3 men who forbid marriage and advocate abstaining from foods, which God has created to be gratefully shared in by those who believe and know the truth.
2 Thessalonians 2:11-12(NASB)
11 And for this reason God will send upon them a deluding influence so that they might believe what is false,
12 in order that they all may be judged who did not believe the truth, but took pleasure in wickedness.
We can know the truth when we love the Word of God enough to accept it, and it alone in matters of religion.