Moreover, brethren, I declare to you the gospel which I preached to you, which also you received and in which you stand, (2) by which also you are saved, if you hold fast that word which I preached to you – unless you believed in vain. (3) For I delivered to you first of all that which I also received: that Christ died for our sins according to the Scriptures, (4) and that He was buried and that He rose again the third day according to the Scriptures, (5) and that He was seen by Cephas, then by the twelve. (6) After that He was seen by over five hundred brethren at once, of whom the greater part remain to the present, but some have fallen asleep. (7) After that He was seen by James, then by all the apostles. (8) Then last of all He was seen by me also, as by one born out of due time. (9) For I am the least of the apostles, who am not worthy to be called an apostle, because I persecuted the church of God. (10) But by the grace of God I am what I am, and His grace toward me was not in vain; but I labored more abundantly than they all, yet not I, but the grace of God which was with me. (11) Therefore, whether it was I or they, so we preach and so you believed.

The first letter to the corinthians was written by the apostle Paul. In chapter 15 Paul introduces a new subject addressing the errors in Corinth regarding the resurrection of Christ Jesus which some in Corinth denied. Paul is saying the doctrine of resurrection of Christ is the primary principal of the gospel, which he preached and in which our salvation depends; if there is no resurrection, our faith is worthless. Paul presents historical facts of eyewitness testimony – he is not referring to all the physical manifestations of Jesus after the resurrection but selects a few examples.
What is the gospel? There is a great deal in the Bible that is not gospel – it is not just a message telling men how they should behave – It is not a call to repentance or amendment of our ways. It is good news to be believed; we may change our behavior and yet never believe the gospel and consequently never be saved. There is only one gospel and it is God’s revelation to sinful man. Comparing all religious systems with one another and all but Christianity set men trying to save their own souls. But the gospel tells us what God has done for us so that guilty sinners may be saved. It is only through the gospel that man is born again – it is the work of God, not man, and it is done. It is the gospel of the Son of God – the gospel of the risen Christ – and leaves no room whatever for human merit. It is the gospel of grace, not works; if it be of works then it is not of grace.
It is a fact of history that Christ died and “for our sins” is doctrinal and explains that death. Christ took the sinner’s place and the sinner’s judgment. The seal of satisfaction in Christ’s work was His resurrection. Physical resurrection is fundamental to Christianity and there is no contradiction in this. Paul and the other apostles believed and preached the same gospel – and in denying the resurrection some corinthians were pursuing a theology of their own.