Bang! I sprint toward the source of that sound, thinking as I run, “I can’t believe they’ve done it again.” Finding my kids in their room, without asking what happened, I nearly shout, “What were you thinking!? I know, you weren’t thinking. And I know the only thought that crossed your mind was having fun, but some of us are working!” Then, in a huff, I return to my work-from-home laptop.
Change the story. You are listening to the news and hear about that politician you dislike. After a few minutes, you mutter to yourself, “That person is out to ruin our nation. I know what he wants, and it is vile and wicked! Always about the money . . .”
What Does the Bible Say About Presumption?
Common to each of these stories is frustration and conclusions based upon the thoughts and wants of other human beings. But wait! How did I or you gain access to the hearts of other people?
Learning to spot this subtle sin in our lives will help us grow in Christlikeness and love others.
Is that possible? Scripture teaches us that both of these stories are examples of an insidious species of pride—presumption. Learning to spot this subtle sin in our lives will help us grow in Christlikeness and love others.
The apostle Paul assumes that we know intuitively that it is impossible for us to know someone else’s heart or thoughts without them being revealed. In 1 Corinthians 2:6–16, Paul explains that he does “speak wisdom but not wisdom from this age” (v. 6), and this wisdom “had been hidden in mystery” (v. 7). Because it was hidden, not one of the rulers of this age could understand it (vv. 8–9)! However, Paul could understand and teach it because “God revealed it to us through the Spirit” (2:10). The Spirit is important, Paul writes, because “the Spirit searches all things, even the deep things of God” (v. 10 cf. Romans 11:33; Ephesians 3:18).
Pay attention to what Paul does next. He gives the reason we should know that the Spirit is necessary to grasp the things revealed to us about God, and he does it with a question. Paul writes, “For who among men knows the deep things of a person except the spirit of that person which is in him?” (v. 11). The anticipated answer is—no one! Paul assumes that we know intuitively that we cannot know a person’s heart or thoughts unless they are revealed to us by that person.  Just like I can’t know your heart, I can’t know the deep things of God without the revealing work of the Spirit.
Why Paul Assumes
Let’s press in and ask why Paul assumes that we know this. Why should we? We should for two reasons: (1) it is our commonsense experience, and more importantly, (2) God revealed this truth in various ways in Scripture. Regarding common sense, we have all experienced times when we intended something, and someone else misunderstood our heart. They couldn’t grasp our intentions until we revealed them by telling them what we were really thinking and wanting.
What Does the Old Testament Say About Presumption?
Regarding the Old Testament, consider the following examples:
- It is God’s prerogative to reveal deep and hidden things (Daniel 2:22).
- Zophar states that Job could not know the deep things of God, which only God knows (Job 11:7–8).
- The hearts of men are open to the Lord (Deuteronomy 8:2; Proverbs 15:11; Jeremiah 17:10).
- While discerning our ultimate motives is difficult for us, God knows them and judges accordingly (Jeremiah 17:9). 
- With help from a person of understanding who is skillful at drawing out our intentions with good questions, we can discern our heart (Proverbs 20:5 cf. 27:19).
- The Lord not only knows all hearts but properly judges them (Proverbs 21:2; 24:12; 1 Samuel 16:7).
From the Old Testament, we see that God is the only one who knows the hearts of all people and who knows himself completely. We learn that we need others’ help to discern our own hearts.
What Does the New Testament Say About Presumption?
These things are confirmed by the New Testament:
- The apostles prayed, “Lord, you are the heart-knower of all people” (Acts 1:24). 
- Peter said, “God—the heart-knower—testified about them by giving them the Holy Spirit” (Acts 15:8).
- Jesus taught, “God knows your hearts” (Luke 16:15).
- Jesus, strikingly, can perceive the hearts and thoughts of men (Mark 2:8; 8:17; Luke 5:22; 9:47) during his earthly ministry.
- Apostles and those specifically filled by the Spirit discern hearts (Acts 5:3–4; 7:39, 15; 8:21).
- Thoughts of the heart need to be “revealed” (Luke 2:35).
- The Lord “will disclose the purposes of the heart” (1 Corinthians 4:5).
- God’s word discerns “thoughts and intentions of the heart” (Hebrews 4:12).
- Jesus tells John that “I am he who searches minds and hearts” (Revelation 2:23).
From the New Testament, we see confirmed that God alone is the heart-knower. Other than the three persons of the Trinity, only those specifically filled with the Spirit are able to know the hearts and intentions of others without talking with them.
What Do We Get Wrong When We Presume?
Where does this leave us? Recall our stories from the beginning. When I rushed into my kids’ room, I presumed I knew their hearts and told them off. I was sinning. The same goes for your imaginary grumbling about a politician whose heart you claim to know though you have never spoken to them.
Presumption does not think the best of others, but the best of ourselves.
What do we get wrong when we presume? Simply put, we elevate our powers of discernment and insight to the level of God. Remember, God alone knows the heart! Presumption does not think the best of others, but the best of ourselves.
How Should We Identify and Avoid Presumption?
The way forward is twofold: (1) learning to listen and (2) combatting with prayer.
Ask Questions and Listen Wisely
The way forward is twofold. First, we need to write Proverbs 20:5 on the tablet of our hearts: “The purpose in a man’s heart is like deep water, but a man of understanding will draw it out.” If we want to understand others and help them understand themselves, we must live like “a man of understanding” (cf. Proverbs 2:2–6, this only comes from the Lord), and we must work on our drawing ability.
This metaphor involves drawing water from the well of “deep water” that is another’s heart, and such drawing work will require patience, understanding, the ability to ask good questions, and the ability to listen wisely to the answers. Asking questions will both help you assume the posture of a “man of understanding” who isn’t presuming they know another’s heart, and it will begin to draw out what the other person meant and thought. For example, my frustration with my kids would have gone very differently had I asked upon entering their room, “Girls, where did that noise come from? What were you wanting to accomplish?”
Fight Presumption as Sin
Second, we need to pray the beginning of Psalm 19:13 regularly, “Keep back your servant also from presumptuous sins; let them not have dominion over me!” The next time you have the thought “I know what they really want,” stop yourself right there and pray Psalm 19:13. Then, live out Proverbs 20:5 and seek to do the hard work of drawing out what that person really means. This is doing unto others what you would want them to do for you. Do not give in to the temptation to be lazy and presume you know their heart because—Scripture everywhere testifies—God is the only heart-knower, and you are not him.
 I should clarify the difference between my main point and what Jesus teaches in Matthew 7:17–20: “Every healthy tree bears good fruit, but the diseased tree bears bad fruit. A healthy tree cannot bear bad fruit, nor can a diseased tree bear good fruit. … Thus, you will recognize them by their fruits.” In context, Jesus is illustrating that from what comes out of a person you may discern the type/kind of heart they have (cf. Matthew 15:7–19; Mark 7:6–23)—in his case, whether or not they are false prophets (Matthew 7:15–16, 21–23). Paul and I are arguing that we cannot fathom the depths of that heart even though we may discern its type (whether of the spiritual or unspiritual [1 Cor 2:12–16]; by which Paul means indwelt by the Spirit or not).
 Read in context, I do not think this passage teaches that everyone’s heart is deceitful. Instead, reading Jer 17:5–10 together, notice the following: (1) there is a contrast between two kinds of people—the cursed man (vv. 5–6) and the blessed man (vv. 7–8) like Psalm 1; (2) in the parallelism between those verses, the heart of the cursed “turns away from the Lord” (v. 5) but the blessed’s “trust is in the Lord” (v. 7); (3) “cursed” and “blessed” are divine actions such that we may mentally add “by the Lord” to them; (4) verses 9–10 describe how the Lord alone knows the heart and is the ultimate judge of all deeds. In other words, Jeremiah 17:9 asks who can fathom the ultimate motives of man (in view of vv. 5–8), and 17:10 answers, only the Lord who justly blesses or curses (cf. Prov 24:12; Rom 2:6).
 The term “heart-knower” in this verse is the first occurrence in Greek literature, and in Scripture, it is only used of God. It appears in Christian literature after the NT, only of God (see, e.g., Hermas, Man. IV, iii, 4; Pseudo-Clement, Homilies 10.13).