Paul in Romans 1 is writing this letter to those that are in Rome, beloved of God, called to be saints. Paul says "that I may be comforted together with you by the mutual faith both of you and me". Does not sound like "all natural men" to me. The ones that he is addressing are "all men" of the church at Rome. He even says that their faith is spoken of throughout the whole world, and you are thinking that he is talking to the natural man that cannot understand what he is talking about. 1 Cor 2:11, The natural man knoweth the things of man by the spirit of man that is in him, and the spiritual man knoweth the things of the Spirit by the Spirit of God that is in him. What is so hard to understand about that? If you were but a natural man, void of the Spirit, you would not be on this forum and discussing spiritual things, because the bible would be foolishness to you.