Ideas about the Kingdom of the Heavens around us and the unity of believers in Christ within it
Korah’s rebellion was to insist on half the truth–that all in the congregation of Israel were holy, set apart to God, because the Lord was among them–but to reject the other half–that only the Lord had the right to assign each their functions. They denied this half of the truth to rebelliously assert their own authority, as false teachers today also do.
Cain’s underlying sin was his arrogant insistence that he could come to God on his own terms. This is the “way of Cain” of which Jude speaks—self-sufficiency, insisting on coming to God on one’s own terms, murderous jealousy of those who truly seek God and are accepted by him, and “repentance” only of the consequences of these sins and not of the sins themselves. It all starts with an attitude of self-sufficiency.