When I said, "the true believer is now in a state of being
'not able to sin,'" I was using the term true believer in its generic theological sense, not as a specific reference to the moniker
@True Believer.
Whether any particular individual is, in fact, a true believer is
not something that can be established with certainty on the basis of empirical evidence. It concerns the inward reality of faith rather than something that can be conclusively demonstrated from outward conduct alone. Consequently, a single act of sin, however serious, does not logically establish that a person's faith was never genuine.
If it did, then St. Peter himself would have to be regarded as a false believer. Yet in many Christian traditions, particularly the Roman Catholic tradition, Peter is understood to have a foundational role in the establishment of the Church, based on Jesus' words:
"You are Peter, and on this rock I will build my church." (Matthew 16:18)
Peter nevertheless denied Jesus 3 times. His denial did not nullify Christ's earlier declaration, nor did it prove that his faith had been counterfeit. On the contrary, at the Last Supper, Jesus foretold both Peter's failure and his restoration:
"I have prayed for you that your faith may not fail. And when you have turned back, strengthen your brothers." (Luke 22:32)
Jesus did not say, "
if you turn back," but "
when you have turned back." Peter's denial was therefore understood not as the absence of genuine faith but as a temporary failure under severe trial. Christ's intercession anticipated both Peter's fall and his restoration, after which Peter would strengthen his fellow disciples.
Peter's example thus illustrates an important distinction:
a believer's identity cannot be conclusively inferred from a single moral lapse, however grave.
However, this is not to suggest that a professed true believer can regard Peter’s example as a license to plunder the grace of God. In many theological frameworks, “true faith” is defined in terms of persevering faith. Within this framework, to be in a state of grace is to be
'able not to sin.' This does not imply that one will not sin, but that sin is no longer unavoidable. A true believer may still sin; but unlike the prior condition of being
'not able not to sin,' the true believer now possesses the genuine capacity to refrain from sin.
On that view, persistent apostasy would be more decisive than a single moral failure, since it would indicate the absence of persevering faith itself rather than a momentary lapse within it.
Peter’s example, then, is not an excuse for sin, but a caution against hastily concluding that a professed true believer’s faith is inauthentic on the basis of an isolated failure.