From where does the idea that Christianity the only true religion come? Other religions claim the same. What is the basis for the Christian claim?
At one level, this question is easily answerable.
Christianity is based upon the idea that Jesus is who He claimed to be. And He said, in John 14:6
I am the way and the truth and the life. No one comes to the Father except through me.
And if Jesus is who He claimed to be, then Christianity must be the only true religion, because He said specifically "No one comes to the Father except through me".
At another level, there are other answers, but too large to fit in a single answer here.
If you're looking for external evidence, there's an entire field of study, known as Apologetics that seeks to provide a defense for the veracity of Christianity, its teachings, the identity of God, and the Truth of the Bible.
There are volumes of information available (as well as counter-points arguing against the Truth of Christianity). Put simply, there's much too much information to make your question answerable in this forum. A Google search for "Apologetics," however, is a good place to start.
Logically, there can only be one true religion. If it is, indeed, true that Jesus is the Eternal Son of God, the Second Person of the Trinity, who became a man when He was born of a virgin 2,000 years ago, lived a sinless life, died a vicarious death and rose from the dead, and if it is, indeed, true that salvation is available to mankind through faith in Him, then Christianity is, in fact, the truth. (I understand that this does not define the beliefs of all that are accepted as Christian on this site.)
Therefore, any religion that claims that Jesus is not any of those things is not true, if, in fact, Jesus really is all of those things.
If Jesus is the Eternal Son of God, then any religion that does not teach that is in error. If Jesus became a man through the virgin birth, then any religion that does not teach that is wrong.
So, Christianity makes truth claims and claims that those claims are actually true (of course). Every other religion does the same thing, so every religion claims that their set of truth claims are, indeed, the ones that are true.
If Christ is indeed the Divine Human (fully God and fully Man) there can be no other, and thus no other religion could lay claim to one who truly knows God and can bring us to him because he is God.
Given that Christianity is the cult of said Jesus Christ, it would follow that if Christians were true to him, they would have a genuine connection to God, and not merely man's reaching up toward him.
I tried making this a bit short but every time found that whatever that is there is relevant for question.
Christianity gets this tag from its scripture itself and the Divinity of Jesus. A Test for a true religion can be on two counts:
To know how it directs its adherents in this earthly life.
And to know how convincing is its claim of everlasting after-life.
To know the answers for these two premises, we need not look further than the respective religious scriptures and get to know what they depicts, for scripture is like genome of any religious belief.
First Premise: A true religion, irrespective of its ultimate aim of bringing all humanity under its fold, will ensure equality, peace, love, justice etc. to all humanity irrespective of cast, creed or religion.
So a true religion needs to have such a scripture, which clearly states these characteristics of “goodness for all” and become a force for good, making this world a better place for all humans in their earthly life. A religion will evidently exhibit this trait of “goodness for all” if exists in its scripture in a manner it deals with all other humans and also this trait is noticeable to the would-be adherents from the scripture itself.
[A note of caution: Whether every follower of any religion will follow or has followed in the past, of what is spelled out in their scripture is a different matter since that would be due to the weakness of human nature not scripture. But what is to be judged is, whether in first place, the scripture has this in its content or not. If any of the religious scripture does not teach these traits of “goodness” to their neighbor, irrespective of cast, creed or religion or has content that teaches otherwise (to hate, to kill etc. etc) (whether to their followers or non followers), then how would anyone can expect the followers/adherents of that religion to practice it and attempt to bring peace, equality and happiness in the society.]
So if you apply this test to the New Testament, (Not Old testament because that stage was like molding and preparing God’s chosen people into special people compared to others, for receiving the Messiah in the world) and if you weigh it against message of any other religion, the message taught by Jesus is beyond any comparison as well as it is unique.
Scripture of other religion may teach their followers all that is good. But Christianity stands apart in a sense that it teaches to love your neighbor to the extent of loving your enemy. It teaches to be humble, be servant not masters and so on (Matt. 5:38-48, Matt. 7:1-5, Matt 22:39-40). Jesus Himself practiced all this and mingled with sinners, rode on a donkey, washed His disciples’ feet and so on. It teaches that it is the patient that needs a doctor not a healthy man and that Jesus came to seek the sinners not the righteous (Mark 2:13-17, Matt. 9:9-13). Imagine, God with His immense love for you, comes searching you, so as to reform and save you from hell. These are the revolutionary teachings which no other religion has in their scriptures which strengthens the claim that the Good News that Jesus preached is Divinely inspired and much relevant to lead an earthly life in peace will all humans.
Second Premise: If we take the case of some of the major religions in the world, the eastern religions (Hinduism) teach that you can become fully “enlightened” through a reincarnation process by doing enough good deeds. Islam teaches you must follow the teachings of the Qu'ran and the Hadiths and accept Mohammad as God's true prophet for the hope that Allah may grant you entrance into paradise. We see that all these religions began with founders (Mohammad, Buddha, Krishna, etc.) who lived and died too. They never said that they are from above except Jesus.
Jesus taught that He was God in the flesh, who came to Earth in human form to die for the sins of mankind, so that “whosoever would believe on Him would not perish, but have everlasting life”. So whatever Jesus said about salvation and after life is like hearing from God Himself (Horse’s mouth). [If one wants to know the truth regarding any event/incident, it is always trustworthy to hear from the Horse’s mouth rather than from the third or fourth eye witnesses]
Jesus is the only “religious leader” who actually claimed to be God on Earth, in the flesh. Of course, He was the Son of God while in human flesh, and yet also fully God and fully human. With this claim from Jesus, Christianity easily proves that it is a true a religion.
This is what we find in the Christian scripture to support the claim of Jesus. In Isaiah 9:6 it is prophesied the Messiah that comes to Earth in the flesh will be called “Mighty God, everlasting Father”. See Isaiah 7:14 also. Also John 3:31, John 6:41, John 8:23-24, John 10:30, John 8:58 and John 11:25. Gospel of John we find verses that clearly depicts Divinity of Jesus.
Jesus is the only founder of any religion who allowed himself to be worshiped as recorded in places such as John 9:38 and Matthew 14:33. In the Old Testament we see that God is a jealous God and declares that no one besides God is to be worshiped, so for Jesus to allow Himself to be worshiped establishes that He did in fact consider Himself to be God.
Jesus backed up His claims by doing things no regular human being was able to do and He did it with a claim that He is same as God, unlike Moses who did it with the help of God. He changed the weather with his spoken word, walked on water, changed water into wine, instantly healed the blind, the deaf, the paralyzed, created fish and bread to feed thousands, brought the dead back to life. In spite of these awesome supernatural powers He never tried to take control of either people or political system forcibly. On the contrary He shunned it as is seen at John 6:15.
Christians claim Christianity is the only true religion because
Its adherents believe it to be so, and their belief stems from their religion's ability to withstand the most thoroughgoing and grueling investigations into its truth claims and yet emerge unscathed. In other words, apologetically, it stands alone.
Christianity is the only religion (at least of which I am aware) whose founder rose from the dead. In other words, the empty grave is powerful evidence--perhaps the most powerful evidence--of its veracity.
Jesus said He was the one, the only, and the only true way to God (John 14:6).
Ear- and eyewitnesses to the life and teachings of Jesus of Nazareth (we call them apostles; see Acts 1:21,22) also claimed Jesus was the only way to God:
"For there is one God and one mediator between God and men, the man Christ Jesus," 1 Timothy 2:5 NIV, said Paul the apostle.
The evidence of radically changed lives bears witness to its veracity. Other religions can claim they create transformed lives, but few if any of their adherents can claim with full assurance that they know they are forgiven of all their sins and that they will be in heaven when they die. The adherents of most, if not all, world religions do not have this full assurance. Some far-eastern religions do not even teach there is an afterlife, at least in the way Christianity does, in that death to them is but a conduit either to nothingness or absorption into nature and/or God, who permeates nature (which is the essence of pantheism).
In an era of what is called "the new tolerance," Christians are unashamedly intolerant of usurpers to Christianity's rightful place at the pinnacle of all the world's religions, including humanism and even the religion consisting of no religion at all! I cite this source as an excellent introduction to how Christians can defend themselves against the charge which is frequently leveled at them that they are intolerant, the assumption being, of course, that intolerance is perhaps the "worst" sin of all.
In conclusion, if I am correct in detecting between the lines of your question the concern about whether Christians are being intolerant by claiming Jesus is the only true way to God, I have two things to say:
First, Christians do not claim (at least I hope they do not) that none of the world's religions have no truth whatsoever. Christians believe, as do I, that
All truth is God's truth, wherever it may be found.
The major world religions have made such inroads into the minds, hearts, and cultures of people groups precisely because they contain elements of truth. Most, if not all, religions would never have gotten off the ground if they had no truth whatsoever to offer their adherents. These religions attract adherents, at least in part, because they offer some truth.
Christians therefore need to be aware of at least some of the aspects of the world's religions with which they can agree, if only to provide a basis for identifying with the people to whom they bear witness of the truth as it is found in its fullness in Jesus of Nazareth.
Second, As Hank Hanegraaff observed in the article to which I provided a citation above,
"Christians must exemplify tolerance without sacrificing truth. Indeed, tolerance when it comes to personal relationships is a virtue, but tolerance when it comes to truth is a travesty."
“Christian religion” is “the faithful observance of the teachings of Jesus Christ and His apostles.”
James 1:27: Religion that is pure and undefiled before God, the Father, is this: to visit orphans and widows in their affliction, and to keep oneself unstained from the world.
Care for the needy and personal virtue are externals which are present when one has a true love for God. The very fact that James is speaking of “pure and faultless” religion, there exist an “unclean and imperfect” type of religion as well—a religion not based on love for God.
Many good practices that we have today in the world and some of which have been conveniently adopted by some other religion have their roots in Christian religion. That is why Christian religion is better than other religion and observing the teachings of Jesus Christ is better than not observing them.
Jesus Christ is the Way to God.
That which leads to God is better than that which leads away from God. We have sinfully wandered away from God. Jesus is the guide that leads us back to God.
Isaiah 53:6 All we like sheep have gone astray; we have turned—every one—to his own way; and the LORD has laid on him the iniquity of us all.
Jesus is that Way, the One who came to seek the lost:
Luke 19:10 For the Son of Man came to seek and to save the lost.”
He is, in fact, God Himself in human flesh, so to find Jesus is to find God:
John 14:9 Jesus said to him, “Have I been with you so long, and you still do not know me, Philip? Whoever has seen me has seen the Father. How can you say, ‘Show us the Father’?
Jesus Christ is the Truth.
The Christian religion is truer than other religions because things that are true are better than things that are false. Jesus is “the Truth” and He is the embodiment of truth, the revelation of God to humanity. The Christian religion is grounded in truth, being based on a historical Person whose acts were verified by eyewitnesses and recorded by four different biographers. In following Christ, Christians have the utmost regard for truth, as opposed to hollow externals and the hypocrisy of false appearances. The Christian religion is unique in that it forces us to face the truth about ourselves and speak the truth with others.
Jesus Christ is the Life.
The Christian religion is true religion because life is better than death. A religion whose leader is still alive compared to religions whose leaders have all died. Jesus is “the Life”; He is the source of life, and without Him one cannot truly live (John 1:4;3:36;5:24;10:10). Jesus provides what we need: the Bread that satisfies forever (John 6:35), the Water that gives eternal life (John 4:14;7:37-38), and the Resurrection and the Life (John 11:25). These are not empty claims; Jesus proved His ability to give life by raising from the dead Lazarus (John 11), Jairus’ daughter (Mark 5), and the boy from Nain (Luke 7). Then, after His own death on the cross, Jesus rose again the third day.
Jesus Christ transforms mankind.
The Christian religion is true religion because righteousness is better than wickedness. Other religions may impose conformity to a certain code of behavior, but they have no power to change the heart. Christianity teaches that the believer is “dead to sin” and now lives “in newness of life” (Romans 6:2,4). The Christian’s zeal for doing good has resulted in the founding of countless orphanages, hospitals, clinics, schools, homeless shelters, and emergency relief agencies—all in the name of Christ. The Christian religion is unique in that it does not force change from without but revolutionizes lives from within.
Jesus Christ is loving.
The Christian religion is true religion because love is better than the absence of love. Jesus showed His love for us in providing for our salvation by dying on the cross (John 15:13). Jesus gave His followers a new command: “Love one another. As I have loved you, so you must love one another. By this all men will know that you are my disciples, if you love one another” (John 13:34-35). Christianity is unique in that it is not a system of rules but a celebration of unselfish love.
As pointed out already frequently, the claim obviously comes from the bible. However whether that makes it a valid claim or not is interesting to ponder:
As most other religions, Christianity is self referential: By definition, you are Christian because you believe in Jesus, and since you believe in Jesus you are Christian.
The same line of reasoning applies for pretty much all other religions as well. "I believe in Zeus and therefore I'm a Hellenist". "I believe in Tenri-O-no-Mikoto and therefore I am a Tenrikyo"
Most religions do have an exclusion clause the explicitly declares other religions and gods invalid. In Christianity that's, for example, the first commandment (second commandment in the Talmud) "Thou shalt have no other gods before me" . Interestingly, the wording seems to imply that other gods do exist, you are simply required to stay away from them.
Once you make this fundamental believe statement, the rest follows easily. For a "Christian" the claim is true "because it says so in the bible". For a non-Christian the bible is irrelevant and the claim cannot be substantiated.
Ravi Zacharias has to say following on this question. From one of his video talk, here is the transcript:
...Take a look at other world religion and see how these four question are dealt with: Origin, meaning, morality and destiny. These four questions are to be answered in two ways. Every particular answer has to correspond to truth, either through empirical form of measurement or through the logical reasoning process and when those four answers are put together they must cohere and not be incoherent. So the two tests should be correspondence and coherence. Only in Judaeo-Christian worldview will you find these four questions answered with corresponding truthfulness and with a coherence of world view.
In the Koran, it is the only historically claimed document that denied Jesus Christ was actually crucified and died on the cross. It denies it. The Greek historians say that he died on the cross, Roman historians say that, Pagan historians says that, Jewish historians says that and Christians historians says that. So historically it is making an affirmation that is really historically untrue.
Origin, meaning, morality and destiny: the Judea-Christian view is not the only one to claim exclusivity but is the only one that takes those four questions with corresponding answers that are truthful and coherent answers that stands the test of time. And the ultimate answer:The resurrection of the dead, that gives you the hope and meaning....