1 Timothy 4:1
1But the Spirit says expressly that in later times some will fall away from the faith, paying attention to seducing spirits and doctrines of demons,
The Spirit expressly says: this is not Paul’s hunch. Later times are already inside the gospel age, as Wesley heard. Some will fall away from the faith—a leaving, not a label for every disagreement.
Departure is possible because faith is a living hold that can be abandoned. Deceitful spirits and demonic teachings explain how: the church is not only arguing with bad ideas, but resisting a lying spiritual campaign. Grace that can be received can also be refused; this verse is one of the pastoral alarms.
The Spirit speaks expressly: Calvin treated this as clear prophecy, not a rumor. Later times name the last days in which the church already lives.
Some fall away as the reprobate make their unbelief public, or as a visible church is winnowed. Seducing spirits and doctrines of demons are true; God is not surprised. The warning still functions as a means: the elect are kept, in part, by taking this alarm to heart.