If we want to know what rational right thinking is all about, we need to look to God. He reveals Himself and His will to man in such a clear and concise manner that the only right response is to fall before Him in worship and adoration.
The apostle Paul was directed by God to spend 11 chapters revealing the plan of God to the readers. All of that was under the inspiration of the Holy Ghost. Based on that clear and just revelation from God through Paul, now God is calling on those who are saved to give the only right response. The word translated as “beseech” means “to urge” or “to admonish”. It is important to note that God is not begging those who are saved to do what He says here. God does not need to beg for anything. He is speaking here in the sense that this is the only legitimate response that a saved person can make, based on all the doctrine that God has given in the previous chapters. There can be no other right response to all that God has declared.
We notice here as well that the word “therefore” connects the following with that which has come before. God does not work in a vacuum. He lays out the truth in a very understandable way. God does expect man to respond in a humble and right way. He holds man accountable for his response as well.
We also see that Paul is writing to brethren here. Unbelievers will not respond properly to God, unless they respond in repentance and are saved. Those who are saved must then respond as God requires. It is contrary to the new nature to do anything other than what God says.
We have already noted that those who are saved are saved by the mercy of God. No one has the right to salvation. The lost Jews of Paul’s day assumed they had certain rights with God that the Gentiles were not “good” enough to have. The Pharisees had this same position, both during the time that Jesus was on earth and after that. For the most part, they were hardened in their sin and they refused to bow before the true God. The odd one like Paul (Saul) was genuinely converted.
The obvious response to the mercies of God is to present our bodies a living sacrifice. The Christian life is for the here and now and it extends into eternity beyond the grave. However, it starts at the moment of salvation. It is the right thing for the saved person to give their life in service to the true God that saved them. A living sacrifice submits to God’s will and serves Him now.
We are also shown that we can know if we are yielding our bodies a living sacrifice to God. We must be holy. We have seen that throughout this letter and we see this throughout the Bible. Holiness is not humanly possible. The “holiness” movement that is found in some religions is contrary to the Word of God. That holiness is not holiness at all. All they do is redefine sin by a humanistic standard. The standard of holiness is God. Peter was directed to write:

I Peter 1:15 But as he which hath called you is holy, so be ye holy in all manner of conversation;
16 Because it is written, Be ye holy; for I am holy.

The holiness that God requires is not the means of salvation. It is the fruit of salvation. God has changed the heart and nature of every saved person. With that changed heart and nature, we can and we must be holy. We must see the importance of being free from sin. Of course, no true child of God can claim to be free from sin. We need to work toward that in the power of the Holy Spirit Who indwells the true child of God.
If we seek to be holy, we will be acceptable to God. No sin can enter into God’s presence. If the true child of God wants to avoid being chastened by God, he or she must submit to the will of God. God promises to chasten every one of His children. He requires that His child bring forth the peaceable fruit of righteousness.
God is not asking anything unreasonable of us. He saves us. He gives His child the power to be called a son of God. He provides the Holy Spirit to indwell every true child of God. He has given us His Word. He has given us all that is needful to be able to serve God properly. It is reasonable for the true child of God to give his life in holy service to God. That is completely reasonable. Cain saw God as being unreasonable. He was a rebel. He was a wicked man. Enoch saw God as reasonable. He walked with God and God took him. He did not grow old and die like all others of his time. He was relatively young for the span of life of that time. He honoured God and God took him out of this world.
The apostle Paul had been saved by the mercy of God. He was told that he would be the apostle to the Gentiles. That was his reasonable service to God as a saved man. He needed to be holy in order to do that. He could not live in sin and be holy. He could not live in sin and please God.
In verse 2 we are reminded that we cannot be conformed to the world if we are saved. We live in the world, but we cannot be a part of the world. The world has a way of trying to draw us into its mold. It tries to entice us in various ways. Some people may be drawn more by the world than others, but we all need to keep the checks and balances in place so that we do not get caught up in the ways of the world.
The only way we can guard against being conformed to this world, is by being transformed. We had our service at a seniors home yesterday. One of the ladies had several questions for me as I was preaching. She has come regularly, but it has been hard to read her. Yesterday she chose to ask questions. I was pleased to see that. It was not a problem for me at all. As she asked questions, I gave Biblical answers. She talked of having her set of beliefs. She had already revealed what some of those were. I told her that is was important for us to be willing to let God change our beliefs if we are saved. Lost people also need to change their beliefs.
The service we had was in a predominantly Catholic home. Their beliefs are far from right. If a Catholic wants to be saved, they must humble themselves as any other person must and they must accept the Biblical fact that there is only one true God and that Jesus Christ is the eternal Son of God and Mary has no place in salvation. She is not the mother of God. We do not pray to her and she does not assist Jesus in providing salvation. From all that she stated, this woman is a lost woman but I believe she is beginning to listen more to the work of the Holy Spirit in her heart. We will continue to pray for her. Lord willing she will be saved and then she can be transformed by the renewing of her mind. Even those who are saved need to change their minds. We do not know everything the moment we are saved. We will never know everything on this earth.
I was raised in a Mennonite tradition. There were some things that they taught properly when I was a child. There were other things they did not teach properly. In order for me to be saved, I needed to take the Word of God as truth and turn to God in repentance and trust in the Lord Jesus Christ as my Saviour. Since I have been saved, there have been many things that I have had to change in my life. There are many things that I was taught that were not Biblical. Some verses that have been very helpful for me are found in II Corinthians 10:3-6 —

II Corinthians 10:3 For though we walk in the flesh, we do not war after the flesh:
4 (For the weapons of our warfare are not carnal, but mighty through God to the pulling down of strong holds;)
5 Casting down imaginations, and every high thing that exalteth itself against the knowledge of God, and bringing into captivity every thought to the obedience of Christ;
6 And having in a readiness to revenge all disobedience, when your obedience is fulfilled.