Part of the ongoing Verse Quick Reference project.
1Jn 3:20 For if our heart condemns us, God is greater than our heart, and knows all things
Calvinist Wayne Grudem writes:
3. Knowledge (Omniscience). God’s knowledge may be defined as follows: God fully knows himself and all things actual and possible in one simple and eternal act.
Elihu says that God is the one “who is perfect in knowledge” (Job 37:16), and John says that God “knows everything” (1 John 3:20). The quality of knowing everything is called omniscience, and because God knows everything, he is said to be omniscient (that is, “all-knowing”).
Wayne Grudem equates John’s phrase “knows everything” with the attribute of knowing all things in “one simple and eternal act”. Basically, this is saying that God’s knowledge is identical to His being, and not composed of parts or distinction.
But the same author who writes that God “knows everything” writes that man “knows everything” in the previous chapter. This is the same phrase:
1Jn 2:20 But you have an anointing from the Holy One, and you know all things.
Instead of taking 1 John 3:20 as “one simple and eternal act” of knowledge, the context is about God knowing people’s hearts. People cannot hide the inner secrets of their hearts from God. There is no reason to think this is a statement about being an “eternal, simple act”. That is highly speculative, and not warranted by the text.
Granted, perhaps John is saying “God knows what you are thinking because God is not lacking any knowledge about anything”. This is a possibility, but there is no reason to arbitrarily extend this “omniscience” to future events. John is not saying “God has known from eternity past what you are going to think”. John is saying “guard yourself, do what is right and put your heart into the right attitude. Because if you do not, and if your heart condemns you, God will know”. The entire context is warding against possible future outcomes. John wants to affect actual change in the life of his hearers. To John, the future was not set.