Anyone can only truly give "Reasons to believe in..." because if anyone could prove what they believed then everyone would believe it--these are issues of faith. As for me, I simply believed, there was no logical deduction, I just believed. If you ask me why I do, I can only say it was because of Him, I heard His voice and followed. Does this perfectly work out in reason? Does Christ make total sense? No, but then that's what the scriptures say as well.
1 Peter 1:20-21 "He was chosen before the creation of the world, but was revealed in these last times for your sake. Through him you believe in God, who raised him from the dead and glorified him, and so your faith and hope are in God."
1 Corinthians 1:18-25 "For the message of the cross is foolishness to those who are perishing, but to us who are being saved it is the power of God. 19For it is written: "I will destroy the wisdom of the wise;
the intelligence of the intelligent I will frustrate."
Where is the wise man? Where is the scholar? Where is the philosopher of this age? Has not God made foolish the wisdom of the world? For since in the wisdom of God the world through its wisdom did not know him, God was pleased through the foolishness of what was preached to save those who believe. Jews demand miraculous signs and Greeks look for wisdom, but we preach Christ crucified: a stumbling block to Jews and foolishness to Gentiles, but to those whom God has called, both Jews and Greeks, Christ the power of God and the wisdom of God. For the foolishness of God is wiser than man's wisdom, and the weakness of God is stronger than man's strength."
So there you go, everyone is at some point part of "those who are perishing" but then God calls, and you can receive Him by faith. For more on that process, see Mark 4:1-29. The fact is that if faith had proof it wouldn't be faith--how could Noah have believed if there had never been rain before that point? The answer is faith, it talks about his faith and that of others throughout scripture in Hebrews 11, where it begins saying:
Hebrews 11:1 "Now faith is the substance of things hoped for, the evidence of things not seen."
Some other translations say "assurance" and "conviction", because the greek words used there actually have a double-meaning and when translating to english you have to pick which one you'll bring focus to. I like this one (NKJV) because it points out our faith as being the very evidence that points to what is not seen, just as Noah's faith was the evidence of the flood to come. I know if you don't believe in Noah you can't use that as a specific reason or anything, but he works as a good example of the principle going on here. It says soon after...
Hebrews 11:3 "By faith we understand that the universe was formed at God's command, so that what is seen was not made out of what was visible."
There are many examples in the New Testament. Making it very clear that the message of the gospel is rejected as foolishness by everyone until God's Spirit convicts them, and if you do not harden your heart to it but believe then there you go. It also says in 1 Corinthians 2 (among othe places) that those who do this are given His Spirit, and you start to see the world in a new way, you start to see the truth in the teachings and evaluate the world in a new way.
Go ahead and say it's stupid if you want, in a way I can see how one would think it is, but then I can't deny what I know is true. It's no longer a concept apart from me that I try and work out logically and decide on, it's something inside me, smething real and of substance. Slightly paradoxal, yes, but so are many things even without believing in God. Nevertheless it is the reason given:
1 John 4:13 "We know that we live in him and he in us, because he has given us of his Spirit."
So how do I believe in one thing by faith but differentiate that between the many number of things I could believe by faith? Scripture keeps one on track, and then there's discernment by God's Spirit, that's about as much as I can figure of it. And yeah you can even get off track on that too, but I suppose you can't honestly follow anything without humility. So you need to be willing to rightly look at how you are living compared to Christ, and change what needs to be changed--As Christ commanded:
Matthew 3:8 "Produce fruit in keeping with repentance."
That fruit is of obedience to His commandments and a well balanced life, and it comes out in your character like this.
Galatians 5:22-26 "But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness and selfcontrol. Against such things there is no law. Those who belong to Christ Jesus have crucified the sinful nature with its passions and desires. Since we live by the Spirit, let us keep in step with the Spirit. Let us not become conceited, provoking and envying each other."
I hope this helps you understand people of faith a bit better.