So far in our series on the fundamentals of the faith, we have examined God the Father, Jesus, and the Holy Spirit. Now we turn to the nature of sin.

Sin exists in the world because of the fall of Adam and Eve. Sin is more than outward behavior or disobedience to God’s commandments. At its core, sin is the desire of humanity to live independently of God. At the core of the unregenerate person lies the Sinful Heart, a heart turned from God and turned toward self. At the core of the believer is the Spiritual Heart, a heart inclined to God and desiring to obey Him.

The heart is deceitful above all things, and desperately sick; who can understand it (Jeremiah. 17:9).

And it shall be a tassel for you to look at and remember all the commandments of the Lord, to do them, not to follow after your own heart and your own eyes, which you are inclined to whore after (Numbers 15:39).

What is sin, and where does it come from?  Ask a child, and he or she will tell you plainly, “Sin is when you do bad things.” For many years, this understanding of sin has pervaded the church. Sin is any violation of God’s law, whether intentional or unintentional. While sin is certainly that, the Bible paints a much broader picture than that.

First, sin begins in the heart. Jesus made it clear when He told the Pharisees that out of the heart the mouth speaks (Matthew 12-34-35). Likewise, the act of hatred, murder and adultery all begin in the heart (Matthew 6:21-28). The implication of that, of course, is that sin doesn’t stay in the heart. Sin will find it’s way out, to dwell in our thoughts, words and actions.

Second, if what Jesus said about the heart and trees bearing fruit after their kind is true, then it follows that the heart of sinful men is sinful. At the core of the unregenerate man is a heart turned toward self. Self seeks its own good, not the good of others, and certainly not the things of God. Paul has another phrase for this: “being in the flesh” (Romans 8:8). He makes it clear that such people cannot please God. To use a well-known saying, they just don’t have it in them.

Under the New Covenant, God has promised to give His people “a new heart and a new Spirit” (Ezekiel 36:26-27). Further, He promised that this new heart would cause His people to walk in His way. He described the transformation as replacing the heart of stone with a heart of flesh. Thus, God was talking about a fundamental change in the nature of His people.

“If that’s true,” you may ask, “then shouldn’t the believer with the new heart be able to walk in God’s ways?” I’m glad you asked that question. We know that our new heart is indeed inclined to obey God. That is one of the strongest personal evidences for the assurance of salvation. If a person says, “I’m a Christian,” yet has no desire to obey the Lord, what might Jesus say about that? Something to ponder.

The answer to the earlier question, though, is a word we mentioned earlier: the flesh. Though the Sinful Heart has been removed and replaced with the Spiritual Heart, what’s left behind is the flesh. The flesh is that part of a person programmed to live independently of God. The flesh, as Paul defines it, resides in the mind (hence the instructions in Romans 12:1-2). The mind has been thoroughly programmed by the heart, so much so that “when I want to do right, evil lies close at hand” (Romams 7:21). The question then becomes how one overcomes sin (which we’ll get to in the future).

At its core, sin is far deeper than flouting God’s laws and decrees. Sin, in its most basic form is embracing the lie that independence from God is freedom and life. As believers, we must reject that lie and embrace the truth that Jesus Christ is freedom and life.