In addressing true knowledge, John Piper in Think, speaks to Paul's words in 1 Cor 8.1-3:
Now concerning food offered to idols: we know that “all of us possess knowledge.” This “knowledge” puffs up, but love builds up. If anyone imagines that he knows something, he does not yet know as he ought to know. But if anyone loves God, he is known by God.
True Knowing Loves People
So the crucial question is: “What would turn this imagined knowing into true knowing?” In other words, what does it mean to know as one ought to know? To think as one ought to think? The answer is in the text before and behind.
Before, Paul had said love builds up (v. 1). That implies that any knowledge that does not stand in the service of love is not real knowing. It is prostituted knowing. It’s as though God put surgical tools in our hands and taught us how to save the sick, but we turned them into a clever juggling act while the patients died. Knowing and thinking exist for the sake of love—for the sake of building people up in faith. Thinking that produces pride instead of love is not true thinking. We only imagine that we are thinking. God does not see it as thinking. It’s not surgery; it’s juggling.
True Knowing Loves God
In seeking to understand what verse 2 means by saying we do “not yet know as [we] ought to know,” I said that the answer is in the text before and behind. We just saw it before in verse 1: “Love builds up.”
Now behind (in v. 3): “But if anyone loves God, he is known by God.” Paul virtually equates knowing as we ought to know with loving God. In connection with verse 1, he makes loving people the criterion of true knowing. And in connection with verse 3, he makes loving God the criterion of true knowing.
Now we see the link between this text and the point of chapter 6 on loving God with all our mind. That’s what the mind is for. And here Paul is saying that loving God is what you are doing when you “know as [you] ought to know.” In his view, thinking and knowing are given to us by God for the purpose of loving God and loving people.
Being Known Is Beneath Knowing
But in verse 3 Paul does not simply relate loving God to knowing as we ought to know. He says, “But if anyone loves God, he is known by God.” What is the point of saying, “He is known by God”? This is parallel to Galatians 4:9: “But now that you have come to know God, or rather to be known by God, how can you turn back again to the weak and worthless elementary principles of the world?” Deeper than knowing God is being known by God. What defines us as Christians is not most profoundly that we have come to know him but that he took note of us and made us his own.
Being known by God is another way of talking about election— God’s freely choosing us for himself, in spite of our not deserving it. It’s the kind of knowing referred to in Amos 3:2: “You only have I known of all the families of the earth.” God had chosen Israel as his people, though they were no better than any others.
What Paul is doing when he says, “If anyone loves God, he is known by God,” is reminding the proud Corinthians that loving God, not loveless knowledge, is the sign of being among the elect.2 He is reminding them that everything they have is owing to God’s free and sovereign initiative. It’s the same as what he had said earlier: “What do you have that you did not receive? If then you received it, why do you boast as if you did not receive it?” (1 Cor. 4:7). The point of verse 3 is that “if a man loves God, this is a sign that God has taken the initiative.”