The debate between peccability and impeccability is conducted among those who all confess that Christ in fact never sinned; it concerns whether He could have. Defenders of peccability argue that genuine temptation requires the real possibility of yielding, and that to deny Christ could sin is to make His temptations a charade and His obedience effortless. Defenders of impeccability—the historic and stronger position—answer that the person of Christ is the divine Son, who cannot sin or deny Himself, and that the union of His sinless humanity with that impeccable person made falling impossible; the temptations were real assaults genuinely resisted, as a real siege may be laid against an impregnable fortress. This is a serious and edifying debate among the orthodox, not a contest between faith and unbelief.

The graver corruption lies outside this family discussion, in the liberal and modernist Christologies that deny the sinlessness of Christ altogether—portraying Him as a great but flawed teacher, a man of his time with the limitations and even errors of any other, who grew morally as we do and was not without fault. This strikes at the heart of the gospel, for only a sinless Savior could be the spotless Lamb, bear the sins of others rather than His own, and provide the perfect righteousness imputed to believers. A sinful Christ would need a Savior Himself and could save no one. The church must therefore guard not only the refined question of impeccability but the foundational truth of His perfect sinlessness, on which the whole work of redemption depends: He who knew no sin was made sin for us, that we might be made the righteousness of God in Him.