We all have one - a heart that is steeped in rebellion. Reformed theology calls is "the total depravity of man".
We see in in children; for many of them "mine" and "no" are among the first words they use.
We see it in teenagers when they learn that they have wings and start to use them - many times in rebellion instead of freedom.
We see it in adults when we observe the "nine you're fine, ten you're mine" rule of speed limits.
I see it in myself. I sleep with a CPAP and I hate it. Most mornings I wake up with the mask laying next to my pillow and a vague recollection of ripping it off my face in the middle of the night. Why? Because I DON'T LIKE IT!
We see it rebellion against parents, against government, against laws, against doctors, against physical limitations.
And it all stems from a rebellion against God.
John Piper writes: When we speak of man's depravity we mean man's natural condition apart from any grace exerted by God to restrain or transform man.
Total depravity does not mean that all people are as bad as they could be - it means that every part of every person is steeped in original sin. Our minds, our will, our emotions, our body - everything. It is all affected by sin.
Scripture tells us of the nature of man.
The heart is deceitful
Jer 17:9 The heart is deceitful above all things, and desperately sick; who can understand it?
People are slaves to sin
Romans 6:20 For when you were slaves of sin, you were free in regard to righteousness.
There is nobody who is righteous.
Romans 3: 10-12 "None is righteous, no, not one; no one understands; no one seeks for God. All have turned aside; together they have become worthless; no one does good, not even one."
We do not accept spiritual things
1 Cor. 2:14 The natural person does not accept the things of the Spirit of God, for they are folly to him, and he is not able to understand them because they are spiritually discerned.
We are dead in sin
Eph. 2:4-5 But God, being rich in mercy, because of the great love with which he loved us, 5even when we were dead in our trespasses, made us alive together with Christ
and were by nature children of wrath, like the rest of mankind. (v.3)
Why are we all thus?
herefore, just as sin came into the world through one man, and death through sin, and so death spread to all men because all sinned— (Romans 5:12)