We note that this statement as well as the following one (v. 7, 8) are objective, are written in the third person. This statement presents the fact regarding what “is impossible” in the case of certain persons. The writer does not say that among his readers there actually are, or that he fears that there are, persons of this kind. His statement constitutes a warning: those once converted may fall so that it becomes “impossible to renew them to repentance.” The readers are to apply that fact to themselves.