ESV - 6 Jesus said to him, "I am the way, and the truth, and the life. No one comes to the Father except through me.
For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
Several years ago I began a protocol together with my wife that went against the world's protocol to help her with her depression. The world's ways were keeping her depressed and suicidal.
Then someone introduced us to another way, literally God's way using a design for which He, God, had designed and destined a company for spiritual warfare.
You may wonder if this adheres to the question or not. I assure you it does.
After several years and after my wife did return to normal, and both still using those products that had done so much for us, I realized that the basis for recognizing the veracity of the company and its products was akin to how I knew, within my own heart, that Christ's message was, in actual fact, the real and actual truth.
Usually there are two sides to any issue. With regards to the products we use, there was the pharmaceutical side and the nutritional side. Then here comes something that is actually God's design, and a new part of the design. God put the right people in place to make this work and the products actually became patented - over 125 to date. With this new message or newly emerging and burgeoning scientific field, it threatened both the pharmaceutical and the nutritional supplement industry. The threat was so great that both sides of the original issue tried to take out this little upstart company with God's design implanted in it and in its main product.
Because the message was new and that it threatened both sides, not being for one side or the other which would have proven to be biased and hence uncertain about its veracity, and since both worked at trying to eliminate the threat and to usurp and use the science and its technology for their own gain or to suppress it in order to keep people in bondage, and the fact that it could not be eliminated is how I know it is the "real deal".
Likewise, Jesus' message back in His day, roughly 2000 or so years ago, threatened the status quo in the land both for the Romans, or Gentiles, and for the Jews, and in particular for the ruling class, the Pharisees and Sanhedrin. Had Jesus' message been seen to be favorable to one side or another, it would have been seen as being biased. There would have been a conflict of interest.
So, because it supported neither one, both were threatened, and in the end, both worked together to try to eradicate Jesus, obviously with no such luck other than for those couple of days.
Because of that joining of opposing forces to attempt to restore their cold war situation because that was what they were familiar with and had come to terms with, the Jewish leaders didn't want to lose their power; and the Romans didn't want a usurper raising the country and incite a rebellion, so they worked together.
That's how I know that Christ's message is real.
When two or more sides of an issue are all threatened by a new message and that threat is seen as being something they all absolutely have to deal with or to lose themselves so that they band together to try to eliminate what they see as the intruder, then the intruder's new threatening message is the right and true message and option.
Christianity is not a religion, it's a covenant. Sealed with the blood of Jesus Christ.
Christianity cannot be proved. It is of faith as is any belief. If I could prove that the Bible and all it teaches is true beyond any doubt, you would be a fool not to put your faith in the God of the Bible. But, if someone could prove just as conclusively that another faith is truer then I would be a fool not to put my faith in it. That is the danger of trying to prove your belief(s). Someone may be a better arguer than you.
I have always thought that Jesus showed the best way: Loving someone into heaven instead of scaring them out of hell.