Summary: How can you tell real doctrine from false? It involves knowing the source of the information and knowing the real thing very well.
In this chapter Paul reveals the source behind the false doctrine that was spreading around Ephesus - commands Timothy to point them out, then encourages him to keep doing the things a pastor does, even if people put him down.
As a pastor in this role Timothy needed:
- A strong sense of the opposition
- Strong convictions of what was true
- Strong leadership skills
- A Strong calling
Not with arrogance and self seeking but self sacrificing and a strong personal integrity.
Here we learn by contrast (the false teachers and some of the church members) and by example (Timothy).
1 The Spirit clearly says that in later times some will abandon the faith and follow deceiving spirits and things taught by demons.
Jesus predicted this:
How does this work? In 2 Chronicles 18 (quickview)  Ahab and Jehoshaphat got together to find out information about a battle they were planning. And the prophet Micaiah told these kings why their prophets were all saying that they would win.
2 Chron 18:18-21 I saw the LORD sitting on his throne with all the host of heaven standing on his right and on his left. 19 And the LORD said, ’Who will entice Ahab king of Israel into attacking Ramoth Gilead and going to his death there?’
"One suggested this, and another that. 20 Finally, a spirit came forward, stood before the LORD and said, ’I will entice him.’
"’By what means?’ the LORD asked. 21 "’I will go and be a lying spirit in the mouths of all his prophets,’ he said.
"’You will succeed in enticing him,’ said the LORD. ’Go and do it.’
Paul also predicted that many would "abandon the faith."
2 Thessalonians 2:10-12 (quickview)  They perish because they refused to love the truth and so be saved. 11 For this reason God sends them a powerful delusion so that they will believe the lie 12 and so that all will be condemned who have not believed the truth but have delighted in wickedness.
"Abandon" is from the word where we get "apostasy" and means to depart from the teachings of the Christian community. Today we find this rampant - people deciding that what the church has believed for thousands of years based on clearly expressed doctrine from the Scriptures is not valid for today. They claim to be Christians but if they depart from the gospel of Jesus they are NOT believers.
Galatians 1:8-9 (quickview)  But even if we or an angel from heaven should preach a gospel other than the one we preached to you, let him be eternally condemned! 9 As we have already said, so now I say again: If anybody is preaching to you a gospel other than what you accepted, let him be eternally condemned!
Look at the source of the lie: "deceiving spirits" and "demons"
Alternate translation: 1 Timothy 4:1 (quickview)  God’s Spirit clearly says (or, states) that in these last days some people will stop believing the Christian teachings; they will instead obey false teachings inspired by lying evil (or, dirty) spirits (or, demons).
So we have two parts - first doubt and then rejection of the gospel, then that opens them up to listen to, heed, and then follow teachings that are inspired by demons. Satan wants people to follow ANY way other than Jesus and has sprouted countless counterfeit religions to hopefully confuse people by shear numbers.