Since Jesus Christ made the claim that He is the only way to God (John 14:6), it follows that either Christianity is true and all other religions are false or that Christianity is false and that one or more other religions may in fact be true. But as the result of Christ's exclusive claim to the truth, Christianity cannot coexist with other religions. I saw a bumper sticker one time that made each letter of the word "coexist" into a symbol of the major world religions. I don't remember all of the symbols used but just that the "X" was the Star of David which represented Judaism while the "T" of course stood for the Cross of Christianity. That's the message of the world; that all religions lead to God and we must learn to coexist by respecting each others beliefs.
Why can't God use many different religions? The simple answer is that God is Sovereign and can do anything He wants. Maybe He could very well have chosen to use other religions but the fact is He did not. He ordained that His Son would receive all the glory and be the only access to Him. God sent His Son and only sent His Son to be the Savior of the world. Therefore, since God ordained that His Son would be the only Savior then no invented religion of man can substitute. How could we possibly override God's will and invent some other way to get to Him?
There are several reasons why I believe Christ is the only way to God and that Christianity is the only true religion. Mine is not a "blind" faith. Many people accuse God of not giving enough evidence to believe. But, as I believe we will learn, this is not the case. Other religions demand their followers to just take them at their word in spite of lack of substance. In other words, there is no evidence to what they claim to be true yet they expect loyalty from their disciples. This is the essence of "blind" faith.
The unity of Scripture
One of the most incredible evidences for the truth of Christianity is the unity of Scripture. The Bible consists of 66 books written by more than 40 authors over a 1500 year time span. And the running theme of the entire work is Jesus Christ. There is no explanation other than God is the overseer and author of it. How could dozens of men from different occupations, in different locations, and at different times in history write a unified book?
The Bible was not written in a vacuum; it is true history. In other words, it is not a volume of "wise" sayings or teachings from some sage or religious leader. It is God intervening into actual world history. The men who wrote it did not just live in a cave somewhere and record their philosophical thoughts. They were prophets, priests and kings called out by God who changed the history of Israel which in turn affected the surrounding world. The entire history of the world has been shaped by these men.
Christianity is not an offshoot of Judaism. Many believe that the Old Testament is the foundation for Judaism and that the New Testament church is a branch from it. But Judaism, like all other religions, tries to earn its way to heaven. It is just another man made religion which was invented by the nation of Israel. Christ is the theme of the entire Bible and His church is the end result of the work He started in the beginning. God has always saved His people by their faith, not by the works of the Law of Moses or any other religious works.
No religion other than Christianity has genuinely fulfilled prophecies as their basis. Some religions claim to have prophecies but miserably fall short of substantiating them. Even the most famous of the false prophets in the world, Nostradomus, gave predictions that are entirely too vague. Not only are his predictions vague but they have nothing to do with the redemption of man. They are just empty sayings that are supposedly fulfilled in modern events.
Now the enemies of Christ have made up reasons to try and explain away the fulfilled prophecies of the Bible. One of these is that the Scriptures were altered to make it look like they were truly fulfilled. But the discovery of the Dead Sea scrolls in 1949 proved otherwise. These Old Testament documents actually pre-date Christ proving the authenticity of the prophecies they contain.
Another excuse they promote is that the prophecies of the Bible are too vague. But this simply is not true. The events surrounding the birth, life, death, burial and resurrection of Christ foretold in the Old Testament were a mystery and were "hidden." Therefore, the prophecies flow within the narration of Scirpture. But this was all in God's plan. It may be that the reason God "hid" the prophecies until after their fulfillment was so that there would never be a doubt that the events came to pass by God alone without the help of any man. Plus, we are told, if man had understood ahead of time what was supposed to take place then it may very well not have happened at all, "Which none of the rulers of this age knew; for had they known, they would not have crucified the Lord of glory" (1 Cor. 2:8).
A miracle is supernatural intervention into this natural world. It is God doing something only God can do. Christianity was confirmed to be true by multitudes of miracles performed by Christ. Just to name a few of Christ's miracles: changed water into wine (John 2:6-10); healed diseases (Matt. 4:23, 24; Luke 6:17-19); cast out devils (Mark 1:34); raised the dead (Matt. 9:25; John 11:43, 44); restored sight to the blind (John 9:1-7); fed the multitudes (Matt. 14:15-21, 15:32-38); walked on water (Matt. 8:26, 27); calmed a storm (Mark 4:39).
Christ not only claimed to be the way, the truth, and the life (John 14:6) but backed up His claim by the miracles He performed. He does not expect us to simply take Him at His word without any proof. In fact, speaking of His miraculous works, He said, "Believe Me that I am in the Father and the Father in Me, or else believe Me for the sake of the works themselves" (John 14:11). He was stating that His miracles give us the evidence we need to believe.
Christ's resurrection from the dead is the basis for our faith (1 Cor. 15:14). To somehow disprove the resurrection would destroy the entire foundation of Christianity. On the other hand, proving it as an actual historical event establishes the Christian faith throughout all ages.
There are several legitimate evidences for Christ's resurrection: the empty tomb; multitudes of eyewitnesses; the outpouring of the Holy Spirit on the day of Pentecost; miracles performed by the apostles; the silence of critics. Without going into detail about each of these, it is sufficient to say that these provide ample evidence for Christ's resurrection as an historical event. And His resurrection proves that He is the only way to God because He is the only man to win the victory over death.
The most reasonable world view
It just makes sense that for a religion to be true then it must answer the crux of life's spiritual questions such as the creation, death, sin, righteousness, and love. But not only should it address the spiritual but also the issues of daily life like family, marriage, divorce, money, work, politics and ministry. No other religion touches on so many areas of life than the Bible.
I know a lady who is diligently seeking the one true religion among many. Along with my wife witnessing to her about Christ, she is also being pursued by a Muslim who gave her a Koran. One day she read in it that it is acceptable for a man to beat his wife. This really turned her off to that religion and rightly so. We need to recognize that the Bible portrays men and women in their proper roles and gives dignity to both.
Some people try to test God by stating that if He is real then why does He not just show Himself or else give us overwhelming evidence of His existence and His will. Actually, God is not obligated to give us anything at all. It is His own prerogative to do as He pleases. But He did choose to show Himself to us in the Person of His Son Jesus Christ. He said, "He who has seen Me has seen the Father" (John 14:9). And in order that we would have strong faith, He gave us not only sufficient evidence but also overwhelming evidence of Him. All the evidence we need is right there in Scripture and mankind is left without excuse.