I grew up as a young Christian during a heyday of Christian apologetics -- Josh MacDowell's Evidence that Demands A Verdict, C. S. Lewis' works, Paul Little's Know Why You Believe, and other various collegiate ministries. But I feel, strongly, we U.S. Christians have gotten away from that sort of positive training, and we have sunken deep into an empty fog of generic positivity.
The Bible never asks us to believe in Jesus because of how He makes us feel. Three of the four gospels are eye-witness testimonials to Christ's birth, life, death, and resurrection. Luke's gospel, which is not Luke's eye-witness account, is a compilation of his research about Christ, drawn from other eye-witnesses whom he interviewed. In these four gospels, the writers cite Old Testament prophecies about the Messiah, which Jesus fulfilled. Matthew begins with a genealogy of Jesus going back to Abraham; Luke 3 gives another, parallel genealogy going back to the first man, Adam.
None of this is warm devotional reading, but it wasn't written so you would feel. It was written so that you would believe.
It alarms me how many Christians believe or disbelieve things based on who says it. If a statement comes from a certain news source, a certain type of person automatically rejects it. But if a statement comes from an opposing news source, they automatically accept it. Do we realize this is approach is how the enemies of Christ justify their rejection of Him? They claim "the authors of the gospels were biased because they believed in Him, so therefore they can't be trusted." In other words, because the gospel writers come from a certain tribe, they can't be trusted.
But this is unsound. Yes, some people do show themselves to be more trustworthy than other people. We should not blindly believe everything we hear. But what matters is why someone believes what they believe. So what that the writers of the gospels were already convinced Christians? So what they weren't neutral? Are convinced people not allowed to speak? A rule such as, "You cannot believe anything you hear from a convinced person" would wipe out pretty much every book, magazine article, website, and TEDS talk known to man.
The two real questions are, is each writer credible, and how well does he make his case? This is why God arranged for there to be four gospels, not just one. The first three gospels give us a synopsis of Jesus' birth, life, and ministry, and the fourth, John, fills in blanks with new material.
In addition, the four gospels stand on the foundation of the Old Testament. They don't exist in isolation from what came before. This is why a recent call from a prominent preacher that Christians should "unhitch" from the Old Testament is profoundly wrong. There can be no believable gospels apart from the Old Testament. We would not be able to make any sense out of the gospels without the Old Testament. The Old Testament is how we know we haven't deceived ourselves regarding Jesus.
At Christmastime, I urge you to purge your heart of the world's way of thinking. Don't believe things because they make you feel good. Don't believe things because someone from your favorite tribe -- whether it's your denomination, your club, your party, your sub-reddit group, whatever -- said it. Believe in Jesus Christ because the testimonies about Him are true. One writer of the past said he did not believe in Christianity because it was socially uplifting, or moral, or psychologically wholesome. He believed because it was true.