Theology in 3D

A Deceitful and Desperately Sick Heart?

Ken Casillas | April 1, 2019
New Testament, Old Testament, Theology

In this post I want to challenge a common use of a biblical text. I’ve used it this way myself, and preachers often do. It’s Jeremiah 17:9:

The heart is deceitful above all things, and desperately sick [“wicked,” KJV]; who can understand it?

This statement joins texts like Genesis 6:5 and Ephesians 4:17–19 in portraying the miserable depths of human depravity. In fact, all three of these passages describe the sinfulness of the human heart specifically. In such passages the terms for “heart” (Hebrew leb and lebab; Greek kardia) speak of man’s internal “control center,” the seat of his inclinations and desires, the core of his being. It should come as no surprise that the Bible would describe the heart of the unregenerate as deceitful and “incurably bad” (NET). But do such descriptions also apply to the heart of the regenerate?


I’m not so sure, and here are some reasons why.

  • If we’re going to apply Jeremiah 17:9 to believers, we should do the same with parallel statements in the context. Verse 1 says, “The sin of Judah is written with a pen of iron; with a point of diamond it is engraved on the tablet of their heart, and on the horns of their altars.” Does that describe the core of a regenerate person’s being?
  • Jeremiah himself gave the solution to the problem of 17:9. The New Covenant he predicted includes the promise, “I will put my law within them, and I will write it on their hearts” (31:34).
  • Ezekiel’s New Covenant prophecies explain this further. “And I will give them one heart, and a new spirit I will put within them. I will remove the heart of stone from their flesh and give them a heart of flesh, that they may walk in my statutes and keep my rules and obey them. And they shall be my people, and I will be their God” (11:19-20; cf. 36:26–27). Ezekiel immediately gives the alternative: “But as for those whose heart goes after their detestable things and their abominations, I will bring their deeds upon their own heads, declares the Lord GOD” (11:21). It sounds like people would have one kind of heart or the other, not both.
  • Unless you are of the more extreme dispensational variety, you probably understand that in some sense Christians enjoy the spiritual blessings of the New Covenant—including a new heart (2 Cor 3; Heb 8:7ff; 10:16ff).
  • Again setting aside dispensational debates, surely the Beatitudes speak to the spiritual condition of Christians. These include the expression “pure in heart” (Matt 5:8; cf. 2 Tim 2:22).
  • Saving faith involves retaining God’s word “in an honest and good heart” (Luke 8:15).
  • God cleanses our hearts by faith (Acts 15:9).
  • Conversion involves becoming obedient to the gospel from the heart (Rom 6:17).


You could do a search for “heart” in Scripture and find other passages confirming that the Christian has a new, good heart and providing a variety of images for and explanations of it. But perhaps other biblical passages are already flooding your mind with counterarguments. For instance, James says that we sin when we are enticed by our own desires (1:13–14). How does that fit in with the idea of a new heart?

The key is defining our terms, and especially the apostle Paul’s specialized use of the flesh(sarx). Paul presents the Christian life as an ongoing tension between the Spirit and the flesh (Gal 5:17). For him the flesh is an influence or force that inclines us to disobedience, the whole package of sinful desires inside of us—what older writers called “indwelling sin” or “the remnants of sin” within the believer. Before conversion we were “in the flesh,” under its sway (Rom 8:8–9). But our union with Christ in his death and resurrection broke the authority of sin (and the corresponding flesh), and now we can resist its influence (Rom 6:1–14). We do this through the power of the Holy Spirit (Rom 8:13; Gal 5:17ff).

The point is that “the heart” is not the same as “the flesh.” The new heart is what we fundamentally are inside, a defining aspect of our identity in Christ. The flesh is a vicious enemy that lives inside us. Paul makes this clear in the distinction he makes in Romans 7:18: “For I know that nothing good dwells in me, that is, in my flesh” (emphasis added).


You might say, “OK, I get it, but when I say I have a deceitful and wicked heart, I’m talking about my flesh, all these selfish desires in me. What difference does it make what I call it? Isn’t this just about semantics?” My initial response would be that we ought to stick as closely as possible to the language of Scripture, which is the language God chose to communicate with us. Maybe I’m not thinking of some biblical usages of “heart” language that would complicate my argument. If so, feel free to post a comment and let me know. How, for example, could we integrate Proverbs 28:26 with the above? One clue: see Ecclesiastes 11:9–10. I feel another blogpost coming on. . . .

At any rate, assuming my argument stands, it actually does make a practical difference how we use our terms. How would you rather view yourself? As fundamentally rotten to your core, with access to divine energy to overcome yourself? Or as having a new and pure heart that is oriented toward God and capable of rejecting the demands of the deposed tyrant within you? Plus, what would become of the “Wordless Book Song”?

My heart was dark with sin until the Savior came in.
His precious blood I know has washed me white as snow.
And in God’s Word I’m told I’ll walk the street of gold.
To grow in Christ every day, I read my Bible and pray.

7 responses to “A Deceitful and Desperately Sick Heart?”

  1. Josh Jensen says:

    Thanks, Pastor Ken. I have often preached (especially to Jarai Christians) that our greatest enemy is our own heart. I plan to be more circumspect in the future, once I figure out how to say “flesh”!

    I’ve read James Jordan argue that the new heart promised in the New Covenant is Jesus himself, and the promise is corporate (a new heart will be given to Israel -> God’s New Covenant people). It seems to me that the promise can be simultaneously corporate and individual, and it makes good sense to see the new heart as “Christ in you”, mediated by the presence of the Holy Spirit. Jordan then says that talk of “new nature” or “change of nature” misses the mark, since the Biblical emphasis is on the direct presence and activity of God Himself in and among His people.

    • Ken Casillas says:

      Hi Josh, thanks for the note! I also have questions/concerns about the “nature” language. Jordan is right in that Paul talks about Christ in us and Peter talks about our receiving the divine nature and John talks about God’s seed being in us. But with you, I don’t see why this would be a corporate or only corporate thing.

  2. Kristian Romer says:

    Interesting, well-written article, Dr. Casillas!

    I agree that we indeed have a new heart in Christ that is capable of rejecting sin. After all, we are not in bondage to sin anymore, as we were before our conversion.

    At the same time, I am not sure that this is an either-or thing. Is it not also true that we are fundamentally rotten to our core (flesh)? In other words, we have this war within us between the totally corrupt flesh and the new, revived heart.

    In Christ we are truly able to live lives of obedience. However, I am afraid that such a dichotomy (i.e., either rotten core or pure heart), where the second option is of course the more desirable one, will lead us to de-emphasize, or even neglect, the power that sin (flesh, rotten core, etc.) still has in our lives.

    Let me know what you think. Especially, let me know if I misunderstood you!

    • Ken Casillas says:

      Thanks for the note, Kristian! I certainly don’t want to minimize the power of sin/the flesh. I’m just trying to use the labels/categories the way Scripture does, with the resulting emphasis. As far as the heart is concerned, Ezekiel 11 does sound like a dichotomy. However, please let me know if you find verses that clearly speak of the believer’s “heart” in negative terms.

  3. Glen says:

    Psalm 51 King David asks for an undivided heart after being under sins sway and power.
    David was regenerate/new heart before his fall from grace. He needed Nathan to help him with the blindness of his own heart and actions.

  4. Glen says:

    Correction please feel free to edit : David prays for an undivided heart in psalm 86:11

    The reference to his heart as whole but divided at war within him. Paul explains more fully in Galatians making distinctions between Spirit and Flesh but here in psalm 86:11 is the ref to heart only.

  5. Dee says:

    After reading all posts I have to conclude that the great Apostle Paul said it all when he declared, “I die daily…” we battle with even the new heart filled at conversion because unfortunately we deal with our carnality on a daily basis. Development of a daily prayer life subdued or keeps in check our “flesh”, we remain full of the Spirit, thereby leaving no room for the “flesh” to take over.

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