So uhhhhhh, half of people who call themselves "Christian" aren't saved?
That's correct.
"Not everyone who says to me, ‘Lord, Lord,' will enter the kingdom of heaven, but only the one who does the will of my Father who is in heaven. Many will say to me on that day, ‘Lord, Lord, did we not prophesy in your name and in your name drive out demons and in your name perform many miracles?’ Then I will tell them plainly, ‘I never knew you. Away from me, you evildoers!’" (Matthew 7:21-23)
What, in your opinion, is the least you have to do to get saved?
Can you answer the question without applying "There is more to Christianity than salvation" arguments?
As just demonstrated by Christ Himself in the Scripture above, our repentance is required. It is precisely why the Gospel message was preceded by John with the exclamation "Repent, for the Kingdom of Heaven is near! (Matthew 3:2)" Then by Jesus, again, in Matthew 4:17. Do not let anyone tell you that preaching a message of repentance is another Gospel; a Gospel with no repentance is another Gospel, and it is one that will ensure your damnation.
While the patience, grace and forgiveness of God through Jesus Christ are free gifts for the one who truly accepts them (Ephesians 2:8-9), they are given
for something; that is, to accomplish something in the believer. Salvation does not end at justification, but merely begins there. Once we are saved from the just wrath of God, if our submission for Christ's salvation and Lordship is genuine, we are then saved
from sin,
to repentance towards Christ,
for good works. As the Scriptures say: "For we are God's handiwork, created in Christ Jesus to do good works, which God prepared in advance for us to do (Ephesians 2:10)." "Or do you show contempt for the riches of His kindness, forbearance and patience, not realizing that God’s kindness is intended to lead you to repentance (Romans 2:4)?" "Therefore, if anyone is in Christ, the new creation has come: The old has gone, the new is here! (2 Corinthians 5:17, see also Galatians 6:15)"
Jesus declared: "I am the vine; you are the branches.
If you remain in me and I in you, you will bear much fruit; apart from me you can do nothing.
If you do not remain in me, you are like a branch that is thrown away and withers; such branches are picked up, thrown into the fire and burned (John 15:5-6)."
In Jesus' explanation of His parable of the sower, He designated that there are four kinds of seed (Matthew 13:19-23). Only one kind He mentions are those who immediately reject the Gospel, and one kind are those who accept it and become fruitful, up to thirty, sixty or a hundred times what was sown. But two kinds of these seeds are described as ostensible believers, those who at once appear to accept it with joy, but then shortly after fall away or get choked by the worries and pleasures of this life and become unfruitful (see also Matthew 7:21 and Jude 1:4). So again we see that there is a distinction between mere intellectual assent to the claims of the Gospel, and having a saving faith in Christ that is authenticated by the bearing of fruit. You can believe in God and that Jesus is His Son and still make yourself an enemy of God by your rejection of His sanctifying work in your life, as even the demons know these truths (Matthew 8:28-29, James 2:19).
So what does Christ mean by bearing fruit? What is this fruit that authenticates that I am remaining in the vine, whom is Jesus? Specific manifestations of the fruit of the Holy Spirit (who Christ does His sanctifying work through, John 16:7) are described in a few places in Scripture (Galatians 5:22-23, 1 Corinthians 12:3-11), but, broadly, the fruit of the Holy Spirit is Christ-likeness. Above all, it is the ever-growing knowledge and love of God, and the consequent growing love for our neighbour.
If we are saved, we have inherited eternal life, and eternal life is to know God (John 17:3), and God is love (1 John 4:8). Thus, if we have come to know God, since Christ makes Him known, (John 1:18) we will love God, and "...this is love for God: to keep his commands. And his commands are not burdensome (1 John 5:3)." This is true; His commands are not burdensome to the one who has come to know God because all of this is the result of the sanctification of the Holy Spirit, who effectuates God's work of saving us from the present power of sin so that we are no longer enslaved to it, but are freed to live for the glory of God. God accomplishes this by giving us an entirely new nature, so that not only do we despise sin, but we also find pleasure in doing the will of God because it is now the Holy Spirit that is at work in us, regenerating our spirit and putting to death the sinful inclinations of our flesh. As Paul admonishes in Galatians 5:16-17:
“So I say, walk by the Spirit, and you will not gratify the desires of the flesh. For the flesh desires what is contrary to the Spirit, and the Spirit what is contrary to the flesh. They are in conflict with each other, so that you are not to do whatever you want.”
This will be gradual, but also eventual; there will be times of regress, but there will be recovery and continual growth, "being confident of this, that He who began a good work in you will carry it on to completion until the day of Christ Jesus (Philippians 1:6)."
In the words of John: "My dear children, I write this to you so that you will not sin. But if anybody does sin, we have an advocate with the Father--Jesus Christ, the Righteous One (1 John 2:1)."
Thus Christ calls to us saying: "Come to Me, all you who labour and are heavy laden, and I will give you rest. Take My yoke upon you and learn from Me, for I am gentle and lowly in heart, and you will find rest for your souls. For My yoke is easy and My burden is light (Matthew 11:28-30)."
Make no mistake: We are saved by grace through faith in Christ alone, but we are saved from the past penalty of sin and the present power of sin
for repentance
to Christ, who will begin His work of making us spotless and without blemish for the day of our glorification, the redemption of our bodies (Ephesians 5:27, Romans 8:23).