Summary: John's Gospel makes it clear that sinner's are responsible for their own unbelief which inevitably leads to condemnation.
Condemned or Not (Read John 3:16-21)
The glorious truth of God’s unfathomable love and His plan of salvation for humanity is stated in John 3:16-17: "For God so loved the world, that He gave His only begotten Son, that whoever believes in Him shall not perish, but have eternal life. 17 "For God did not send the Son into the world to judge the world, but that the world might be saved through Him. “
God clearly did not send His only Son into the world for the purpose of judgment, but rather, His purpose was to save the world through the life and death of the Son. The passive voice is used in the phrase “that the world might be saved”, indicating that the world is saved from an outside source of deliverance, namely God Himself, by sending the Son. God brings spiritual and eternal deliverance through the instrumentality of the One, Unique, Son Jesus.
The reason for Jesus’ coming from Heaven in the flesh was to save, but judgment is also indicated: “That whoever believes in Him shall not perish but have eternal life”: Eternal Life for ALL WHO BELIEVE is contrasted with those who will “perish”, so what happens to those who have not or will not believe? They will die eternally because there is ONLY forgiveness and life IN GOD’S Provision of the Son sent from God.
The Great Divide
Look at verse 18: "He who believes in Him is not judged; he who does not believe has been judged already, because he has not believed in the name of the only begotten Son of God.” He who believes (in the present tense) into Him is not judged (also in the present tense). The person who believes is in a continual habitual state of “believing in Him” and is not judged as a present ongoing activity of God.
The person who does NOT believe (in the present) already has been judged. The person who does not believe is in a continual habitual state of “NOT BELIEVING” and stands under a settled state of condemnation and judgment of God that will eventually yield its final results. Ongoing unbelief results in condemnation AS the person lives in this state of unbelief. It will be consummated, not with eternal life but with eternal punishment. WHY? “Because he has not believed in (or into) the name of the only begotten Son of God.” Unbelief causes condemnation or judgment while the unbeliever lives. God has set forth Jesus as the only WORTHY OBJECT OF ONES BELIEF/FAITH. The ultimate evidence that Jesus alone is the only object of faith is that God raised Jesus from the dead. Rejection of Jesus in favor of another way to God rejects God’s Choice that the person of JESUS ALONE MUST BE THE WORTHY OBJECT of one’s settled belief and trust.
Not believing in Jesus alone as Savior and Lord is equivalent to self-condemnation; God is not to be blamed but rather the unbeliever who remains in his sin. Human beings remain responsible and God does not compel anyone to believe, but everyone born into this world and born in sin faces the necessity of escaping an already existing condemnation against them. In verses 1-8, the focus was on the necessity of the “new birth” or “birth from God”; in verses 12-18 the emphasis is on believing. The verbs in verse 18, “has been judged” and “has not believed” accentuate the settled state of the unbeliever’s condemnation because of their own unbelief.