This noun emphasizes purity, integrity, and sincerity—moral cleanness that flows from undivided devotion. In 2 Corinthians 6:6, Paul lists it among credentials of his ministry alongside knowledge, patience, and kindness—qualities that authenticate apostolic service. In 2 Corinthians 11:3, Paul fears the Corinthians may lose 'the purity and sincerity toward Christ' through seduction by false teaching, just as Eve was deceived. The word denotes not merely external moral correctness but inner integrity, singleness of heart, unmixed devotion. It's the quality of one whose motives are pure, whose allegiance is undivided.