1 Corinthians 15:22

For as in Adam all die, even so in Christ shall all be made alive (KJV)

Then: People use metaphors to explain ideas. God uses events as metaphors for spiritual truth. So when Paul used these words to vocalize God's plan for salvation, the Corinthians could intuitively grasp its meaning and importance. The concept of salvation was not new to the Corinthians because they'd already been through the struggle of fighting sin and accepting Christ. They had to have been eager to receive this clear explanation. God works through history using events as a way to teach his purpose. For mankind, focused on our place in the center, everything needs to make sense from this point of view. At first all was perfection, then came the fall, but in the end, perfection will reign again. For a long time mankind lived with the hope of a Messiah. With the coming of Christ into the world that hope is explained and reinforced. The resurrection validated God's plan.

Now: "In Adam's fall, we sinned all" was a rhyme in the New England Primer which was used to teach the alphabet and religious principles concurrently. Illiteracy (not being able to read) was the devil's way of keeping people from knowing what the Bible said. Each generation has its own problems with biblical understandings. Believing that there is good in everybody, some cannot grasp the concept that all men are fundamentally flawed. They kick against a different goad than Paul's, but it still classifies as kicking. It took Paul a long time to understand. So too the rest of us. Eventually those who know that Christ is, the Holy Spirit is to be trusted, and God's judgement is sure, do accept that as we all died with the first sin and were pushed out of the Garden, with Christ's punishment, death and resurrection, we can all reenter eternal life.