The electing love of God the Father, the life and death of Jesus Christ, the God-man, and the faith placed in our hearts by God the Holy Spirit teach the truth of the Trinity. The Trinity accomplishes our salvation. The message of grace alone, Christ alone, and faith alone presupposes man's utter lostness. The alone underlines the fact that the fallen sinner can make no contribution to his salvation. The price of redemption, even the blood of the Lord of glory, makes it clear that every ordinary human work is valueless to procure salvation.
Grace alone means to be accepted in spite of being unacceptable.
Christ alone means that we have absolutely no righteousness before God but Jesus Christ. Faith alone means that we confess that the only thing about us which is good is that God has pronounced us good out of sheer mercy toward us and out of sheer justice for Jesus Christ. Sin cost Adam and Eve their home in Paradise and a son torn from them by the murderer's hand. It cost the Jews their beloved city and their children who were carried away by rapacious armies. But even that could but dimly portray the cost of sin.