1 Corinthians 15:45-47 And so it is written, The first man Adam was made a living soul; the last Adam was made a quickening spirit.
Howbeit that was not first which is spiritual, but that which is natural; and afterward that which is spiritual.
The first man is of the earth, earthy: the second man is the Lord from heaven.

QUESTION: "When one becomes a Christian has the OLD MAN (who we are in Adam) been eradicated, put to death, or not?"

This is a very important question, one that the Scriptures can answer.
The Scriptures contain The Doctrine of Two Men: The first man who is represented by Adam, and the second man who is represented by Christ. (1 Cor.15:45-47 above)
They also contain The Doctrine of Two Positions: The first position which represents "Death" because of sin which gets its power to kill through the "Law", and the second position which represents "Life" because of righteousness that comes by "Grace" which operates through faith. (read Romans 6:1-10)

To put it simply, either a man is IN Christ ( and therefore "Born Again") and has entered the Position of grace and spiritual life, OR a man is Not in or of Christ at all (but is born once of the flesh, of Adam only) and therefore remains in the Cursed Position of being under the Law and eternal spiritual death (unless something is done to solve that).

So when the First Man (Adam) sinned he died POSITIONALLY! He died to God in every way, body, soul and spirit. Once he died Positionally before God he began to die experientially on this earth as well. Not only was he dead Positionally Speaking before God, even his body began to decay and die as well (Genesis 5:5).

This was the inevitable outcome of his chosing a Position of death. His SIN (which came because of his unbelief in what God told him) had cut him off from God's righteousness, and because we (the whole human race) were in his genes, we too have inherited his fallen nature by birth, only to die Positionally as well just as Adam had. Therefore it matters not how good or bad any of us is that gets us into heaven, but whether one is in or out of Christ. So when ADAM fell ALL MEN fell!

What needs to be understood is not the workings of the man born once, but of the man born twice! Why does the Christian DIE; rather, why does his body die, right along with everyone else? This seems to be a great paradox? However, if we are; Positionally Speaking IN Christ, then our sins have been forgiven, we have been born again. Now we stand before God just as if we have never sinned, and ever a brand new creation. (Again, all thanks to Christ!) So what is going on? If Christ has paid for all of our sins then why does the Christian's body still die?

The most important thing to remember is that at the cross God proved that He is DONE, FINISHED with this world and all of its kingdoms! Because of sin none of what's left is worth saving or fixing up again, and He is letting it all run down, naturally (only intervening here and there through Grace). He is on a mission - it is His will to usher in a new kingdom ruled by His Son, one who's inhabitants have eternal life and who obey Him on earth as they do in heaven and who walk with Him and honor Him in Spirit and in Truth (as He is).

Again this means that He is not interested in making this world (this present age) paradise any longer. The evidence is clear. Because of sin this world, along with our bodies (Christian and non-Christian alike) are decaying and dying. He is after a New Man made in His image along with a New World, one where righteousness reigns! When the time comes for this New heaven and earth to begin it will mark the end of this present age.

Once one is Born Again of God, Positionally Speaking, they are taken and placed, body, soul and spirit into The Second Adam (who is Christ). In Him is Life Eternal. But at this present time Eternal Life only applies to our soul and spirit. The body (in its present state) cannot inherit the promises of God at this time, because in this life, in this world, SIN and DEATH are still present in it and still at work and everything is running down (i.e. "dying"). However, our mortal bodies will inherit eternal life at the coming of Christ, when all of those who Keep His words will be changed in the twinkling of an eye.

In this present world (or age) there is no escape from Physical Death for any of us believers, except by the return of Christ (1Thes.4:17). Our present bodies will become spiritual - immortal WHEN we receive our New Bodies at Christ's coming (1 Cor. 15:42-44).

Through faith in Christ there is promised escape from soul death and spiritual death (i.e. "separation from God"), but nothing is promised to preserve our body from death and decay for thousands of years in this life. In life or death we await our New bodies at the ushering in of the new kingdom age (when death will be destroyed) because (as Paul says)...

Now this I say, brethren, that flesh and blood cannot inherit the kingdom of God; neither does corruption inherit incorruption.
Behold, I show you a mystery; We shall not all sleep, but we shall all be changed,
In a moment, in the twinkling of an eye, at the last trump: for the trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed.
For this corruptible must put on incorruption, and this mortal must put on immortality.
So when this corruptible shall have put on incorruption, and this mortal shall have put on immortality, then shall be brought to pass the saying that is written, Death is swallowed up in victory.
O death, where is your sting? O grave, where is your victory?
The sting of death is sin; and the strength of sin is the law.
But thanks be to God, who gives us the victory through our Lord Jesus Christ. 1 Corinthians 15:50-57

That we should receive NEW bodies at Christ's visible appearance is founded upon the Hope of the Gospel... Read Romans 8:19-25.

It should also be noted that the Scriptures say that, "The sting of death (that which gives it its hurt) is sin, and the strength of sin is the law" (1 Cor. 15: 56). This means that where there is no death because of sin there is no sting or hurt because of it either. And if we have been crucified with Christ (Gal.2:2) then death has lost its sting, seeing that Christ has tasted death for every man (Heb.2:9). Our faith in Christ has ended our Spiritual Death - or - Old, Sinful Position before God. Now we know that the Scriptures say that the just shall walk by faith and not by sight (2 Cor. 5:4-8), therefore The Sting of death applies to ones soul and/or spirit, and not to their bodies.

To prove the Scriptures are true in this case let's take a look at Hebrews 9:28 and Acts 7:59-60...
So Christ was once offered to bear the sins of many; and unto them that look for him shall he appear the second time without sin unto salvation.

And they stoned Stephen, calling upon God, and saying, Lord Jesus, receive my spirit. And he kneeled down, and cried with a loud voice, Lord, lay not this sin to their charge. And when he had said this, he fell asleep (i.e. died).

This doesn't mean that Stephen in his physical body didn't feel any pain as they were stoning him, it means that he simply fell asleep after they had done so. One thing for sure, he wouldn't have to experience the sting, hurt or the power of sin that others experience who die in their sins. The time of Stephen's death is when the Position he stood on by faith became real to his soul and spirit, and right there he entered paradise as a new creation in God.

The scriptures also say that the strength of sin (that which gives sin its power) is the Law. The emphasis of all of this is to prove that where there is no Law there is no sin thus no guilt of sin, therefore there is no power. Let's look at what happened when this "Power or Strength of sin" appeared inside of Paul...

What shall we say then? is the law sin? God forbid. Nay, I had not known sin, but by the law: for I had not known lust, except the law had said, you shall not covet.
But sin, taking occasion by the commandment, worked in me all manner of covetousness. For without the law sin was dead.
For I was alive apart from the law once: but when the commandment came, sin revived, and I died.
And the commandment, which was ordained to life, I found to be unto death.
For sin, taking occasion by the commandment, deceived me, and by it slew me.
Therefore the law is holy, and the commandment holy, and just, and good. Romans 7:7-12

And so the knowledge of sin is made extra powerful, extra spiritual because of the law which says: OBEY ME! In Paul's case it was the law that said: Obey: Thou shalt not covet, that made his his sin exceeding sinful. (In my case it was thou shalt honor thy mother and father.) The harder one tries to keep it the more exceedingly sinful they become until the person realizes that they can't keep it, try, try though they might. Why? Because....

Romans 7:14 For we know that the law is spiritual: but I am carnal, sold under sin. (Also see Romans 7:15-25)

Again look at the Scriptures! They say that without the law there is no sin! So does that mean that if God hadn't given the law there would be no sin? Not at all! What it means is that without the law there would have been no KNOWLEDGE of sin: "Thou shalt not eat of the fruit of that tree"! (The knowledge of sin came when they ate of the tree which gave them knowledge of Good (righteousness) and evil (sin). God gave the law to Adam in Eden (but of this tree thou shalt not eat), and He gave it to the Jews via Moses. He did not give the law to save anyone who tried to obey it, rather He gave the law in order to put men under the condemnation and knowledge of it whenever they broke it! There is no mercy in the law.

To the Christian the Scriptures say:

For I through the law am dead to the law, that I might live unto God.
I am crucified with Christ: nevertheless I live; yet not I, but Christ lives in me: and the life which I now live in the flesh I live by the faith of the Son of God, who loved me, and gave himself for me.
I do not nullify the grace of God: for if righteousness comes by the law, then Christ is dead in vain. Galatians 2:19-21

Again Paul is speaking Positionally in Christ. On the one hand he is dead - he is crucified with Christ - he is dead to the law and its power. This Death of his is actual yet can only be reckoned Positionally Speaking, by understanding thus reckoning oneself as being dead to the law but alive unto Christ... and yet the man lives - Why? - because Christ now lives in him", and Christ cannot live until and unless that person Knows he is a sinner and repents, and his only way out is to become crucified with Christ like Paul.

A man cannot serve both the law and God. The law was given to expose sin and give strength to sin, while God is given to reveal himself in His Grace and Glory. "Once the law was alive and had done its job and slew me, so that the righteousness of Christ (that comes only by faith and not by doing the works of the law) would raise me from the dead", says Paul.

The only way to escape the influences of our sinful nature, flesh, Old Man, is to escape from this body of flesh we live in, (i.e. to die with Christ) Positionally speaking. But until then, Conditionally Speaking in himself he remains a sinner. Outside of Christ the man of flesh (i.e. the man born once) remains a sinner through and through.

But I see another law in my members, warring against the law of my mind, and bringing me into captivity to the law of sin which is in my members.
O wretched man that I am! who shall deliver me from the body of this death?
I thank God through Jesus Christ our Lord. So then with the mind I myself serve the law of God; but with the flesh the law of sin. Romans 7:23-25

Paul understood the relationship between the Spirit and the flesh. He knew the war and struggle that was constantly going on inside him, vying for his affections! Yet this very same Paul had also written Romans 6, and earlier verses of chapter 7, said....

Likewise reckon you also yourselves to be dead indeed unto sin, but alive unto God through Jesus Christ our Lord.
Let not sin therefore reign in your mortal body, that you should obey it in its lusts.
Neither yield your members as instruments of unrighteousness unto sin: but yield yourselves unto God, as those that are alive from the dead, and your members as instruments of righteousness unto God.
For sin shall not have dominion over you: for you are not under the law, but under grace. Romans 6:11-14

Wherefore, my brethren, ye also are become dead to the law by the body of Christ; that ye should be married to another, even to him who is raised from the dead, that we should bring forth fruit unto God.
For when we were in the flesh, the motions of sins, which were by the law, did work in our members to bring forth fruit unto death.
But now we are DELIVERED FROM THE LAW, that being dead wherein we were held; that we should serve in newness of spirit, and not in the oldness of the letter. Romans 7:4-6

Remember that Christ had TWO Natures. In becoming man, flesh, He took hold of His Adamic Nature; or what some call, his human nature, and He submitted it to God by doing His will. In his Sanctified Position before God, Paul was not in the flesh, but IN Christ Jesus (i.e. he walked after the Spirit). Still, in his Present Condition he was also a man of flesh, his Adamic life with their members were still present within him.

However, Paul had been crucified with Christ and he knew it! All that was left was for him to keep on reckoning it so. Paul was no longer a helpless bond-slave to sin; thanks to God crucifying him with Christ, so that he (the new man) should no longer be a slave to sin any longer, doing its bidding....

Knowing this, that our old man is crucified with him, that the body of sin might be destroyed, that we should no longer serve sin. For he that is dead is freed from sin. Romans 6:6-7

Lie not one to another, seeing that you have put off the old man with his deeds; And have put on the new man, that is renewed in knowledge after the image of him that created him: Colossians 3:9-10

So either we; individually, have been crucified with Christ and know it, or we haven't! Do we still serve sin? Do we still practice it? Or have we been renewed in the knowledge of God? Thy Will Be Done!
So what about your Old Man? Do you claim to be sinless, without sin? Has your Old Man been eradicated or not?

POSITIONALLY Speaking we stand perfectly sinless before God!!!....
Whosoever is born of God doth not commit sin; for his seed remaineth in him: and he cannot sin, because he is born of God. 1 John 3:9

But, what about CONDITIONALLY Speaking???....
If we say that we have no sin, we deceive ourselves, and the truth is not in us.
If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.
If we say that we have not sinned, we make him a liar, and his word is not in us. 1 John 1:8-10