Ideas about the Kingdom of the Heavens around us and the unity of believers in Christ within it
Like Balaam, false teachers do their work stealthily motivated by greed. They do not openly deny the Lordship of Christ, but deceptively proclaim teachings that permit us to retain our own independence, greed or lust, to seek first our own pleasure, and still, they say, please God. They teach these things not necessarily because they believe them, but to obtain our following and our money.
In Galatians 5:17-23, “heresies” are one of the works of the flesh–something we do, not something we believe. These works are opposed by the fruit of the Spirit.
Factions, “hereseis,” as used in 1 Corinthians 11:19, clearly does not refer to divisions caused by false teachers. Instead, in that context, it refers to divisions caused by neglect and humiliation of poor believers and by the formation of personality cults.