14 Do not be unequally yoked together with unbelievers. For what fellowship has righteousness with lawlessness? And what communion has light with darkness?
And what communion [partnership] has light [truth] with darkness [falsehood]?
God’s people are the children of the “light.” “Light” refers to divine truth. “Darkness” is any system of belief outside biblical revelation. Non-Christians live in doctrinal and ethical darkness (Eph 5:8; 1 Th 5:4-5). “Communion” means partnership. Christians should not have a common relationship of life and endeavor, which those that reject biblical truth. Shared faith has a bonding characteristic (Php 1:5; 4:15).
Part of the “darkness” in Corinth was the false doctrine of syncretism brought to the church by false teachers. Darkness is anything associated with sin or error, which is Satan’s kingdom.
The light of truth and the darkness of the world system are mutually exclusive.
It is common for people today to infiltrate churches under the guise of tolerance. This is a tool of the devil because it has a propensity to compromise essential doctrine.
Christians operate under the light of Christ shed in their hearts. Non-Christians do not.