Even in his opening salutation, Paul self-identifies as an apostle of Jesus Christ, and then walks the talk, preaching the gospel of a savior promised in the scriptures, descended from David, declared by the Spirit to be God’s son, and raised from the dead.
In the case of Romans, you CAN tell a book by its cover, or at least by its opening paragraph. It is Paul’s summa, his great work of theology and godly living. Excepting perhaps one of the gospels, it may be the most influential book of western civilization. He wrote it in 57 AD, probably in Corinth. He dives right in. I can’t. I don’t have the Spiritual lungpower to stay down so long, marveling at the treasure. The best I can manage is a deep breath, a few strokes down, a quick look, and then it’s back to the surface.
To better understand salvation by grace through faith (v. 17), I must understand man’s depravity. He has willfully rejected the obvious truths of God evident in creation. This wrong turn leads to a long slide at midnight down a cliff of lies. The longer the slide, the faster and messier it gets. From Darwin to gay marriage and plenty in between, you can connect the dots. Paul leaves no room for catching a root and pulling oneself back up the cliff like Indiana Jones. Mankind without grace is in eternal free fall. God throws up his hands and says, “you want filth, then go ahead and wallow in it.”