Total Depravity basically means every aspect of man is tainted and inclined to sin apart from the work of Christ. Sometimes the bible describes this as the "flesh" or being born into a sinful nature. Total depravity doesn't mean we are sinful as we can be. It means our emotions, thoughts, and desires are corrupted by sin. Apart from Christ even our greatest works are like dirty rags. Apart from giving glory to Christ, our "good works" can have alternative motives or intentions to bring glory to ourselves. Even as Christians, we often rob God of his glory by trying to attract glory to ourselves.
The reason I bring this up is because i met with a pastor who eloquently described the gospel in a way i haven't really heard before. We always focus on seeing the glory of God's work on the cross. We see his sovereignty, grace, and forgiveness poured out on his people. However sometimes we miss to see the depravity of our human nature. Isaiah saw God in all his glory and saw the angels worshiping him singing, "Holy, Holy, Holy is the Lord Almighty." Isaiah then falls on his face and cries, "Woe is me, I am ruined. I am a man of unclean lips.." In the instance of seeing God in his holiness, he sees how unworthy, guilty and sinful he is. But an angel tells him that his guilt is taken away and his sin is atoned for.
The point is when we see a fuller image of God and his righteousness, we inevitably see our corrupt sinful nature. We begin to hate our sin. It causes us to have less dependency on our human strength and less confidence in human pride. When we see that we are dead in our sin, unable to do anything good apart from God, it causes us to trust in God's power and grace. The higher we view God and the lower we see any good within ourselves the bigger we see the cross that bridges us.
The Gospel of God's grace is not just a means unto salvation and justification. The Gospel of God's grace is something that we ought to depend on daily for our spiritual sanctification and growth. Our relationship with God is only possible by the atonement of Christ. He enables us to grow in holiness. He gives us a new heart and a new nature. We are no longer a slave to sin, but become slaves to righteousness. The more Christ-like we become the more our nature desires to worship God.
Apart from the vine we can do nothing. If you look at the parable of the prodigal son, the parable is directed to the pharisees and the religious leaders. The second brother was doing things to try and earn his worth from the Father. He felt that his hard work should be paid back from the Father. Instead the Father shows mercy on the son who repented of his foolish ways. In a sense, we are like that second brother who try to do good on our own strength. Often we depend on ourselves rather then trusting in God in order to look good, impress others or bring glory to ourselves. I once heard a friend say, "You know why I think the bible is true? Because if this was fabricated by man then they would have elevated man. Rather they elevated Jesus, and write how stupid, clueless and sinful they are."
When we see the sovereignty and holiness of God and see our total depravity, we shouldn't wallow in despair and condemn ourselves for all our past mistakes. Rather we should trust in the work of Christ. He has forgiven us and absorbed all the wrath our sins deserve. In hearing this good news, we are responsible to respond in faith and in repentance.
The Source
God is the source of all that is good. He replenishes and restores us. I think of how God provided manna for the Israelites. In the same sense, he is our portion and our daily bread. He is the fountain that satisfies us with everlasting water. He overflows our cup with joy. He is the source of true peace, wisdom and power. In Him, we find freedom and contentment. He is a God who heals and comforts. He strengthens and empowers us by His Spirit. He disciplines those he loves. He is the source of all that is good.