Total Depravity: (result of original sin) The doctrine that fallen man is completely touched by sin and that he is completely a sinner. He is not as bad as he could be, but all areas of his being, body, soul, spirit, mind, emotions, etc., are sin-stained. In that sense he is totally depraved.
Because man is depraved, nothing good can come out of him and God must account the righteousness of Christ to him. The sinner cannot save himself nor exercise faith apart from regeneration.
Regeneration: (born-again) The act of God whereby he renews the spiritual condition of a sinner. It is a spiritual change brought about by the work of the Holy Spirit so that the person then possesses new life – eternal life.
Reformed theology teaches that regeneration precedes faith.
Justification: “An instantaneous legal act of God in which he (1) thinks of our sins as forgiven and Christ’s righteousness as belonging to us, and (2) declares us to be righteous in his sight.” -Grudem
Just-as-if-I-never-sinned & Just-as-if-I-had-always-obeyed.
Imputation: To reckon to someone the blessing, curse, debt, etc. of another. Adam's sin is imputed to all people. Therefore, we are effectively all guilty before God. Our sins were put upon, imputed, to Jesus on the cross where He became sin on our behalf and died with them. Therefore, our sins are forgiven.
Imputation is the means of our salvation. When Jesus died on the cross, our sins, in a sense, died with him. The righteousness that was his through his perfect obedience to the Father in his complete obedience to the Law is imputed, given, to us.
Legalism: The view that one finds salvation or God’s favor by the merit of his own efforts to perform works of the law.
Legalism is our default setting regarding how we view God and salvation.
Legalism says that we climb up to God. The Gospel says that God came down to us.
Legalism says “do” to earn favor, the gospel says “it is done” – now live every day in light of that news.
Sovereignty: Supreme reign / supreme power
The right of God to do as he wishes with his creation.
This implies that there is no external influence upon him and that he also has the ability to exercise his power and control according to his will.
Gospel: The good news that though we were by nature enemies of God, we now have forgiveness of our sins through Jesus Christ. He lived a perfect life, died for our sins, was buried, & and bodily rose in accordance with the Old Testament (See 1 Corinthians 15).
”From ‘Genesis to Revelation’ it is God’s promise of a Son that will crush the serpent’s head, forgive the sins of his people, raise them from the dead, and give them everlasting life solely on the basis of his grace for the sake of Christ.” – Horton
Grace: Unmerited favor
“God’s goodness towards those who deserve his punishment.” - Grudem
It is God's free action for the benefit of his people. It is different than justice and mercy. Justice is getting what we deserve. Mercy is not getting what we deserve. Grace is getting what we do not deserve.