In the letter Paul addresses problems in which he had been informed (1 Cor 1:10-6:20), and answers the questions contained in the letter he received (1 Corinthians 7:1-16:9). One issue was ressurection, and more specifically, the bodily ressurrection of Christ Jesus, the future ressurection of those perservering in the gospel, and ressurrection in general. Prior to addressing this issue of resurrection squarely, Paul reminds the Corinthians of the redemptive gospel they received through his preaching (1 Corinthians 15:1), that was taught by the other twelve apostles of Christ Jesus (1 Corinthians 15:11), and that includes the bodily ressurection of Christ Jesus. Paul writes, "Now, brothers I want to remind you of the gospel I preached to you . . . for what I received I passed on to you as of first importance: that Christ died for our sins according to the Scriputres, that he was burried, that he was raised on the third day according to the Scriptures . . . this is what we preach, and this is what you believed" (1 Corinthians 15:1-11). Paul's purpose for reminding the Corinthians was to asert that the redemption of an individual embracing the gospel not only depended on Christ's physical death, but on his bodily ressurection. Moreover, one needs to perservere, or "stand firm" in the gospel he taught them by grace throuh faith. This is clear in the immediate context when comparing "This is what you believed" in 1 Corinthians 15:11b with 1 Corinthians 15:1-2 "Otherwise, you have believed in vain" (1 Corinthians 15:2). In other words, one previously believing must continue in this gospel by grace through faith.   Also compare with Galatians 5:4, Colossians 1:23, & Romans 11:22.

I was confronted with many  hard questions as a result of studying this epistle. Also Compare Galatians 1:8-9 and 2 Corinthians 11:14.