Christians make provisional yet actionable and weighty judgments on whether someone is a Christian based on fruit.

They are provisional because we are open to being wrong. God alone knows with finality the secrets of the heart (Psalm 44:21, Proverbs 21:2). God also knows the final moments of a person’s life.

They are actionable because they affect how we greet, grieve over, celebrate, affirm, pray for, warn, receive, evangelize, enjoy, and encourage (Matthew 5:44, Philippians 1:6, 1 John 3:4-10, Galatians 6:10, John 13:34-35). Knowing whether someone is a believer affects how you relate to them. Knowing whether someone was a believer affects how you remember them.

They are weighty because Christ is present when believers confirm right judgments (John 20:23, Matthew 18:20), including excommunication (1 Corinthians 5:9-13).

They are based on fruit because we are commanded to consider the consistent pattern of a person’s words and works (1 John 3:4-10, Matthew 7:16).

They are to be merciful and patient because we also seek mercy and patience (Matthew 7:2)

They are to be cautious, judicious, and non-hypocritical lest we step on the rake that Jesus warns of in Matthew 7:1-5.