Argument for Universal Salvation:
The Bible says that if you confess "Jesus is Lord", you will be saved.
"That if you confess with your mouth, "Jesus is Lord," and believe in your heart that God raised him from the dead, you will be saved. For it is with your heart that you believe and are justified, and it is with your mouth that you confess and are saved."
(Rom. 1:9-10)
The Bible also says that everyone will confess "Jesus is Lord".
"As surely as I live,' says the Lord, 'every knee will bow before me; every tongue will confess to God"
(Rom. 14:11)
"Therefore God exalted him to the highest place and gave him the name that is above every name, that at the name of Jesus every knee should bow, in heaven and on earth and under the earth, and every tongue confess that Jesus Christ is Lord, to the glory of God the Father."
(Phil. 2:11)
"Therefore wait for me," declares the Lord , "for the day I will stand up to testify. I have decided to assemble the nations, to gather the kingdoms and to pour out my wrath on them- all my fierce anger. The whole world will be consumed by the fire of my jealous anger. "Then will I purify the lips of the peoples, that all of them may call on the name of the Lord and serve him shoulder to shoulder."
(Zeph 3:8-9)
These verses seems to indicate that all are saved because all will confess that Jesus is Lord.
"for God's gifts and his call are irrevocable. Just as you who were at one time disobedient to God have now received mercy as a result of their disobedience, so they too have now become disobedient in order that they too may now receive mercy as a result of God's mercy to you. For God has bound all men over to disobedience so that he may have mercy on them all."
(Rom. 11:29-32)
"This is a trustworthy saying that deserves full acceptance (and for this we labor and strive), that we have put our hope in the living God, who is the Savior of all men, and especially of those who believe."
(1 Tim. 4:9-10)
"For as in Adam all die, so in Christ all will be made alive. But each in his own turn: Christ, the firstfruits; then, when he comes, those who belong to him. Then the end will come, when he hands over the kingdom to God the Father after he has destroyed all dominion, authority and power. For he must reign until he has put all his enemies under his feet. The last enemy to be destroyed is death."
(1 Cor. 15:22-26)
"and through him to reconcile to himself all things, whether things on earth or things in heaven, by making peace through his blood, shed on the cross."
(Col. 1:20)
"I declare to you, brothers, that flesh and blood cannot inherit the kingdom of God, nor does the perishable inherit the imperishable. 51Listen, I tell you a mystery: We will not all sleep, but we will all be changed-- in a flash, in the twinkling of an eye, at the last trumpet. For the trumpet will sound, the dead will be raised imperishable, and we will be changed. For the perishable must clothe itself with the imperishable, and the mortal with immortality. When the perishable has been clothed with the imperishable, and the mortal with immortality, then the saying that is written will come true:'Death has been swallowed up in victory. Where, O death, is your victory? Where, O death, is your sting?'"
(1 Cor. 15:50-55)
"Like water spilled on the ground, which cannot be recovered, so we must die. But God does not take away life; instead, he devises ways so that a banished person may not remain estranged from him."
(2 Sam. 14:14)
"But I, when I am lifted up from the earth, will draw all men to myself."
(John 12:32)
"He is the atoning sacrifice for our sins, and not only for ours but also for the sins of the whole world."
(1 John 2:2)
"Even though I was once a blasphemer and a persecutor and a violent man, I was shown mercy because I acted in ignorance and unbelief."
(1 Tim. 1:13)
"Consequently, just as the result of one trespass was condemnation for all men, so also the result of one act of righteousness was justification that brings life for all men.
(Rom. 5:18)
"He must remain in heaven until the time comes for God to restore everything, as he promised long ago through his holy prophets."
(Acts 3:21)
"All this is from God, who reconciled us to himself through Christ and gave us the ministry of reconciliation: that God was reconciling the world to himself in Christ, not counting men's sins against them. And he has committed to us the message of reconciliation."
(2 Cor. 5:18-19)
"But we see Jesus, who was made a little lower than the angels, now crowned with glory and honor because he suffered death, so that by the grace of God he might taste death for everyone."
(Heb. 2:9)
"The disciples were even more amazed, and said to each other, "Who then can be saved?" Jesus looked at them and said, "With man this is impossible, but not with God; all things are possible with God."
(Mark 10:26-27)
"For men are not cast off by the Lord forever. Though he brings grief, he will show compassion, so great is his unfailing love."
(Lam. 3:31-32)
"Let this be written for a future generation, that a people not yet created may praise the Lord: "The Lord looked down from his sanctuary on high, from heaven he viewed the earth, to hear the groans of the prisoners and release those condemned to death." So the name of the Lord will be declared in Zion and his praise in Jerusalem when the peoples and the kingdoms assemble to worship the Lord."
(Psalm 102:18-22)
"On this mountain he will destroy the shroud that enfolds all peoples, the sheet that covers all nations; he will swallow up death forever. The Sovereign Lord will wipe away the tears from all faces; he will remove the disgrace of his people from all the earth. The Lord has spoken."
(Isa. 25:7-8)
"And he made known to us the mystery of his will according to his good pleasure, which he purposed in Christ, to be put into effect when the times will have reached their fulfillment--to bring all things in heaven and on earth together under one head, even Christ."
(Eph. 1:9-10)
"...and the fire will test the quality of each man's work. If what he has built survives, he will receive his reward. If it is burned up, he will suffer loss; he himself will be saved, but only as one escaping through the flames."
(1 Cor. 3:13-15)(Note: Mark 9:49 and 1 Cor. 5:4-5)
"He will wipe every tear from their eyes. There will be no more death or mourning or crying or pain, for the old order of things has passed away." He who was seated on the throne said, "I am making everything new!" Then he said, "Write this down, for these words are trustworthy and true."
(Rev. 21:4-5)