Many Americans claim to have a personal relationship with God, but how do we know whether they actually do?

First John offers two tests of belonging to God: behaving and believing. How we behave is an ethical test. First John 1:5-2:2, which we will begin studying today, is an example of such a test. How we believe is a theological test, and 1 John 2:20-23 and 4:1-3, which we will study later, are examples of it.

These tests of relationship with God are not only biblical, they are also common sense. Consider your own relationships. If you belong to an association of professionals—whether doctors, lawyers, or teachers—your behavior must conform to a professional code of conduct. Violate that code, and you will be kicked out of the group. Or if you are the best friend of someone, you will hold true beliefs about that person. By contrast, holding false beliefs about that person—not knowing their likes and dislikes, the names of their family members, etc.—probably indicates that you don’t know them as well as you think, if you know them at all. Similarly, belonging to God requires behaving like him and believing the truth about him.

As noted above, 1 John 1:5-2:2 offers an ethical test of relationship with God. Verse 5 tells us about God’s character: “God is light; in him there is no darkness at all.” Verses 6-7 go on to speak of the necessary connection between God’s character and the believer’s behavior:

If we claim to have fellowship with him yet walk in the darkness, we lie and do not live by the truth. But if we walk in the light, as he is in the light, we have fellowship with one another, and the blood of Jesus, his Son, purifies us from all sin.

The issue in these verses is the “claim” of “fellowship with [God].” According to John, this is a testable claim. If people make the claim “yet walk in darkness,” then their claim is empirically false. On the other hand, if people “walk in the light,” then that is evidence that they have “fellowship with one another” (i.e., the church) as well as “fellowship with [God].”

But what happens when we don’t behave like God, when we sin? And let’s be honest here, even life-long, spiritually mature Christians struggle with sin. Do we fall in and out of relationship with God? No, for as John puts it, “the blood of Jesus, [God’s] Son, purifies us from all sin.” We belong to God not because of what we have done for him, but because of what he has done for us through Christ.

But if this is the case, does the ethical test of relationship with God have any real force? If we belong to God regardless of past behavior, does future behavior matter? Absolutely! Christ’s death on the cross “purifies us from all sin.” It sets in motion the process by which our behavior begins to conform to God’s. If we belong to God, then we will behave like him. Or as John puts it, “walk in the light, as God is in the light.”