Christians, when pressed, will often allow a number of concessions to their faith such as;
All meaning, of course, “No you silly head. The New Testament is 100% literal fact! As everyone can plainly see.”
Let's take a look at a few such ideas.
Phrased as a special concession, all Christians must be able to concede that “If Jesus Lied, he wasn't God”. This is because, as everyone knows, God always tells the truth. But if Jesus lied, he would be discredited from being God (let alone the messiah). The same goes for Paul. If Paul was somehow found to be a liar, all of Pauline Christianity would be cast into doubt.
So the point is conceded. It is precisely because a Christian holds it to be true that Jesus did not lie, and that he was perfect, and that Paul was inspired, etc. that they are from God. Another related concession is that if Jesus didn't fulfill the law, he would not have been qualified to be the messiah.
A general category for the notion that if for any reason we need Jesus, if that reason was a) false or b) provided for in another way by God, we would c) not need Jesus. So the topics in this section are intended as responses to “You need Jesus because [reason].”
It is not God's will that we believe in Jesus. It is God's will that we follow his commandments. For example, in Matthew 19, Jesus says:
16 Then someone came to him and said, “Teacher, what good deed must I do to have eternal life?” 17 And he said to him, “Why do you ask me about what is good? There is only one who is good. If you wish to enter into life, keep the commandments.” 18 He said to him, “Which ones?” And Jesus said, “You shall not murder; You shall not commit adultery; You shall not steal; You shall not bear false witness; 19 Honor your father and mother; also, You shall love your neighbor as yourself.” 20 The young man said to him, “I have kept all these;[b] what do I still lack?” 21 Jesus said to him, “If you wish to be perfect, go, sell your possessions, and give the money[c] to the poor, and you will have treasure in heaven; then come, follow me.” 22 When the young man heard this word, he went away grieving, for he had many possessions.Matthew 19:16-22
The answer here is that in order to reverse what Christians call original sin, the “dying you shall die” curse for eating of the Tree of Knowledge of Good and Evil, and have eternal life; one must “keep the commandments”. This is of course repeated many times in the old testament as well, verses will be provided as appropriate.
On the other hand, if it is true that it is God's will that we believe in Jesus, then God would not have told us to simply keep the commandments, but instead he would have actually told us that his will is for us to believe in Jesus. What we actually find when we look at the bible, is that God never says we have to believe in or accept any messiah. We only have to follow his commandments (and then, only those which apply to us).
For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.John 3:16
18 But if I build up again the very things that I once tore down, then I demonstrate that I am a transgressor. 19 For through the law I died to the law, so that I might live to God. I have been crucified with Christ; 20 and it is no longer I who live, but it is Christ who lives in me. And the life I now live in the flesh I live by faith in the Son of God,[g] who loved me and gave himself for me. 21 I do not nullify the grace of God; for if justification[h] comes through the law, then Christ died for nothing.Galatians 2:18-21
Every Christian reading this should understand the idea being responded to here. In short, 'If you don't believe in Jesus, you will not have everlasting life.“ and further that this was all according to God's plan.
Tied in with this is the idea that God loves us; to a Christian, it seems obvious that God gave us Jesus because he loves us; in fact so much as to sacrifice his own son. Christians will draw strong parallels with Issac here. However it must be made clear that by challenging this issue we are absolutely not challenging the idea that God loves us, or that he wants us to be forgiven. We are simply examining the vehicle which God chose for his grace and salvation to be delivered.
Continuing in the theme that God wants everyone to follow his commandments. In the bible, God states the Jews are a light to the nations and that in the end times the world will come to knowledge of God from the Jews. (Please see: A Light to the Nations.
Thus it is our conclusion that it is God's will for us to follow his commandments versus believe in any sort of messiah.
Christians dispute this by stating this is the “old order”, “old covenant” (which was “done away with”), or “Old testament” – and Jesus is brought in by the “New Testament”. Thus we must examine replacement theology.
Also see: Replacement Theology
The notion that the Gentile nations (let alone the Jews) are to be saved via Jesus is problematic because God had already issued his plan of Salvation via the Jews. The Christian position seems to directly contradict what God had said on the subject in the Old Testament.
First is the problem of prophecy. None of the prophets named Jesus, and none of them spoke of a messiah who would be sacrifiecd or who we would have to 'believe in' or 'follow' in order to be saved. The notion of being saved by 'his blood' or any other Christian message is simply absent in the Old Testament. But this is not an idea which has arisen in a vaccum; This claim was not made in the absence of any other reasonable explanation.
13 Yet the Lord warned Israel and Judah by every prophet and every seer, saying, “Turn from your evil ways and keep my commandments and my statutes, in accordance with all the law that I commanded your ancestors and that I sent to you by my servants the prophets.”2 Kings 17:13
As we see, prophets were sent to warn Israel and to guide them to keep the law. To guide and rebuke Israel in it's compliance with the law. One might consider Jonah as an exception, yet Jonah's message was for the city of Nineveh to pray to God and to turn away from their sins (perform teshuvah) – and this in and of itself was a given as a message to the Jews regarding their duty to the gentile nations. So considering Jonah, both the message in the book and the message of the book stand in sharp contrast to the need for vicarious atonement. It is instead a commentary on the Jewish role as a light to the nations.
As an example, Moses' job is established as a prophet by his charge to instruct and guide the people of Israel;
14 God said to Moses, “I am who I am.”[a] He said further, “Thus you shall say to the Israelites, ‘I am has sent me to you.’”Exodus 3:14
God also qualifies future prophets as people who have the words of God put into their mouth. They will be “like Moses” – messengers to the Jewish people.
15 The Lord your God will raise up for you a prophet like me from among your own people; you shall heed such a prophet. 16 This is what you requested of the Lord your God at Horeb on the day of the assembly when you said: “If I hear the voice of the Lord my God any more, or ever again see this great fire, I will die.” 17 Then the Lord replied to me: “They are right in what they have said. 18 I will raise up for them a prophet like you from among their own people; I will put my words in the mouth of the prophet, who shall speak to them everything that I command. 19 Anyone who does not heed the words that the prophet shall speak in my name, I myself will hold accountable.Deuteronomy 18:15-19
This continues the theme that the role of a prophet is to rebuke and guide Israel back to their covenant. Thus, it is difficult to imagine God changing his mind and issuing salvation by alternate means. Further, even considering Jonah, it would serve as an example of how Jewish Law and Teshuva is sufficient for gentile nations, and how it would not be insufficient; as Nineveh was saved.
Christians must concede that God does not require a sacrifice for the remission of sins. See: Does God Require a Sacrifice? which outlines God's salvific plan in the holy scriptures.
Christians will concede that you can be saved if you keep the law but (and this is the hitch, they say,) it is impossible to actually keep the law (for whatever reason), and that is why you need Jesus. For example, Paul says:
10 Now therefore why tempt ye God, to put a yoke upon the neck of the disciples, which neither our fathers nor we were able to bear?Acts 15:10
15 We ourselves are Jews by birth and not Gentile sinners; 16 yet we know that a person is justified not by the works of the law but through faith in Jesus Christ. And we have come to believe in Christ Jesus, so that we might be justified by faith in Christ, and not by doing the works of the law, because no one will be justified by the works of the law. 17 But if, in our effort to be justified in Christ, we ourselves have been found to be sinners, is Christ then a servant of sin? Certainly not! 18 But if I build up again the very things that I once tore down, then I demonstrate that I am a transgressor. 19 For through the law I died to the law, so that I might live to God. I have been crucified with Christ; 20 and it is no longer I who live, but it is Christ who lives in me. And the life I now live in the flesh I live by faith in the Son of God, who loved me and gave himself for me. 21 I do not nullify the grace of God; for if justification comes through the law, then Christ died for nothing.Galatians 2:15-21
(emphasis mine)
From the above and other passages (Romans 9-10-11, and others) it becomes a doctrine of Christianity that no one can keep the law, but rather that God gave the law to the Jews so that they would realize it was impossible to keep.
Interestingly, enough of the early church opposition remains in Peter, John, and James that this is disputed within the New Testament itself; most obviously by James. The case presented by James almost reads like a rebuttal to Galatians as he deals with the same issues in the same order as Paul prevents them, but counters his arguments each time.
3 For the love of God is this, that we obey his commandments. And his commandments are not burdensome.1 John 5:3
11 Surely, this commandment that I am commanding you today is not too hard for you, nor is it too far away. 12 It is not in heaven, that you should say, “Who will go up to heaven for us, and get it for us so that we may hear it and observe it?” 13 Neither is it beyond the sea, that you should say, “Who will cross to the other side of the sea for us, and get it for us so that we may hear it and observe it?” 14 No, the word is very near to you; it is in your mouth and in your heart for you to observe.Deuteronomy 30:11-14
40 Keep his statutes and his commandments, which I am commanding you today for your own well-being and that of your descendants after you, so that you may long remain in the land that the Lord your God is giving you for all time.Deuteronomy 4:40
29 If only they had such a mind as this, to fear me and to keep all my commandments always, so that it might go well with them and with their children forever!Deuteronomy 5:29
17 You must diligently keep the commandments of the Lord your God, and his decrees, and his statutes that he has commanded you. 18 Do what is right and good in the sight of the Lord, so that it may go well with you, and so that you may go in and occupy the good land that the Lord swore to your ancestors to give you,Deuteronomy 6:17-18
12 If you heed these ordinances, by diligently observing them, the Lord your God will maintain with you the covenant loyalty that he swore to your ancestors; 13 he will love you, bless you, and multiply you; he will bless the fruit of your womb and the fruit of your ground, your grain and your wine and your oil, the increase of your cattle and the issue of your flock, in the land that he swore to your ancestors to give you. 14 You shall be the most blessed of peoples, with neither sterility nor barrenness among you or your livestock.Deuteronomy 7:12-14
12 So now, O Israel, what does the Lord your God require of you? Only to fear the Lord your God, to walk in all his ways, to love him, to serve the Lord your God with all your heart and with all your soul, 13 and to keep the commandments of the Lord your God[a] and his decrees that I am commanding you today, for your own well-being. 14 Although heaven and the heaven of heavens belong to the Lord your God, the earth with all that is in it,Deuteronomy 10:12-14
7 The law of the Lord is perfect, reviving the soul; the decrees of the Lord are sure, making wise the simple;Psalm 19:7
Also see: Psalm 119
One of the reasons for Jesus to come in the form of a man was to fulfill the law. Let's leave aside for a moment all other issues besides stating that as his goal. Therefore, in order to be Holy and to fulfill his role he needed to keep the Torah perfectly.
Therefore if we also keep the Torah perfectly, then we will be righteous too. Why? Because God said so in the Hebrew Bible. Christianity predicates itself on the truth of the Hebrew bible; Romans 11 deals with this issue (for exmaple). How can God have broken his promise to the Jews, yet the Christians trust him? So overall, all of God's covenants and promises in the OT must be as valid today as they ever were. So that is why Jesus had to have kept the law in order to be who Christians say he was. Because he had to keep the letter of the law.
So if we also manage (somehow, any how, even hypothetically) to keep the law, we too will be righteous by God. And there are many examples of such righteous people in the bible; Noah, Asa, King David, Hezekiah, even Joseph and Mary (the parents of Jesus), are in the New Testament called righteous. So there it is, you don't need Jesus if you can keep the law perfectly.
Of course, the Christian will tell you why they think it is impossible to do so; but that is a separate issue.
Christians will admit theology from the Oral Law even where it does not conflict with Christian Theology; but will not accept any rabbinical fence despite it being present in the bible.
An example is the story where Abraham smashed the idols – or the story where he was thrown into a furnace by Nimrod. Christians will generally accept these accounts as probable.
It is possible to argue minor points from the oral law so long as they are not rabbinical. The idea is that Israel received many prophets – for example Gabriel came to discuss with Daniel – and during these encounters the angels did not correct any aspect of Jewish tradition (or if they did, the result is what we see today). Even Jesus said that the Pharisees (read: Chazal) sit in the seat of Moses, so you should do all they tell you – simply that you should not act in a hypocritical manner (as they supposedly did).