The title above expresses a formula in logic and mathematics regarding compound statements (i.e., “biconditionals”). The formula (IFF, abbrev.) applies if, and only if both statements are of exactly the same “truth value.” The IFF formula is a powerful way of expressing propositional facts and truths that are incontrovertible.
The New Testament contains several statements that readily demonstrate this formula, but which men deny or ignore on a large scale to their own present and future detriment. Consider the following:
“Except ye believe that I am he, ye shall die in your sins” (John 8:24). One will avoid dying in sin and being eternally condemned if, and only if one believes Jesus’ Deity claims. Those who deny that Jesus is the only begotten of the Father will be lost.
“Except ye repent, ye shall all…perish” (Luke 13:3, 5). One will avoid perishing (eternally) if, and only if one repents of his sins (i.e., turns from them in purpose and in practice). Those who continue in sin will be lost eternally.
“Except one be born of water and the Spirit, he cannot enter into the kingdom of God” (John 3:5). One may/can enter into God’s kingdom (either its earthly or heavenly state) if, and only if one is born of water and the Spirit. Jesus will deliver up to God in the heavenly kingdom only those who are in His kingdom here below (I Corinthians 15:24).
“He that believeth and is baptized shall be saved” (Mark 16:16a). One will be saved from the ravages, guilt, and consequence (both now and in eternity) if, and only if one believes the Gospel and is baptized according to New Testament teaching. All others will not be saved (i.e., they will be lost).
“Repent ye, and be baptized every one of you in the name of Jesus Christ unto the remission of your sins” (Acts 2:38). One will receive remission (forgiveness) of sins if, and only if one repents of his sins and is baptized according to New Testament teaching. Those who fail to do so will arrive at The Judgment with unforgiven sins and will thus be lost.
“He [Jesus] became unto all them that obey him the author of eternal salvation” (Hebrews 5:9). One will receive eternal salvation if, and only if one obeys Jesus Christ. It is not enough merely to believe in Him; one’s salvation depends upon obeying Him.
“Be baptized, and wash away thy sins” (Acts 22:16). One’s sins are washed away if, and only if one is baptized according to New Testament teaching. Baptism is the God-ordained act in which one is cleansed of sin through the blood of Christ (I Peter 1:18–19; Revelation 1:5).
These are but a few of many such statements indicating immutable Truth concerning eternal salvation damnation.