If there is no resurrection, why are faithful Christians the most foolish?
If there is no resurrection from the dead, then Christ is not risen, and preaching and faith are vain. Faithful Christians who devote themselves to churchgoing and Christian activity are most foolish, because they are wasting their time on something that ultimately does not exist.
Les explains that Paul likely encountered Sadducees in Corinth, since the Sadducees rejected resurrection from the dead as foolishness, and some Corinthians were saying there is no resurrection. Paul argues that if there is no resurrection, then Christ is not risen; if Christ is not risen, preaching is vain and faith is vain. Therefore, anyone who ascribes to Christianity and is faithful in churchgoing and Christian activity, if there is no resurrection, is of all people the most foolish, because they are wasting their time. Why sit in the pew and sing the hymns of the faith if there is no resurrection? To Paul, it is foolishness.