Total depravity teaches that the fallenness of our condition affects the radix, the core of our being. It’s a radical thing. There is no part of our humanity that has not been profoundly affected by the fall and by sin. The mind, the heart, the will, the body—the whole person, in totality, has been radically affected by sin. But that affectation does not destroy or annihilate the image of God.
In Noah’s time, God instituted capital punishment for first-degree murder because the person who murders another human being does so to a human being who is made in the image of God (Gen. 9:6). So, there the Bible talks about people after Adam in their fallen condition. Though the image was marred, distorted, blurred, and all the rest, it was not annihilated.
If total depravity meant the total destruction of the imago Dei, the image of God, we wouldn’t be able to add two and two and come up with four. We wouldn’t be able to think at all. We wouldn’t be able to have the faculty of choice. We would have no legitimate affection for anything. If that were the case, our humanity would be destroyed along with the image.