If I went to a car dealership and they had a beat up, old Ford Pinto with a sticker price of $80,000, I would tell the salesman that was an unreasonable price for that car. The car is not worth that amount so it would not be logical to pay that amount.

This definition of reasonable is exactly what Paul has under consideration in Romans 12. When he says that it is our “reasonable” service, he means it is “logical” that we do this.

God has, by His mercy and grace, saved us from our sins and called us into newness of life. In Ephesians chapter 2, we learn that we are created in Christ Jesus UNTO good works. This does not mean that God is causing us to do good works but He is (by the new birth) EQUIPPING us to good works.

Therefore, it is only LOGICAL that, when we realize what God has done for us, we respond by giving our lives to His service every day.