Knowing versus Showing that Christianity is True
Properly Basic Beliefs
There are many things we believe, even though we can't ever prove them, e.g.,
The world has existed more than five minutes. (We could be a brain in a vat with memories implanted in it.)
Laws of Logic. (The law of contradiction, the law of excluded middle, and the law of identity.)
It is wrong to hurt other people for fun.
The testimony of others
These things are called properly basic beliefs.
We have an extremely strong sense that these beliefs are true (even if we can't prove them) and no reason to think that these beliefs are actually false.
Defeaters and Rational Belief
If I become aware of some defeater of one of my properly basic beliefs, then I should give it up (or find a defeater of the defeater).
Oleg and the stars TBD
We might not be absolutely certain they are true, but most people would still want to say we're justified or rational in thinking that they are true.
False Beliefs We Can Identify
We know that some beliefs are not true.
There is no such thing as Truth (self-defeating)
All religions or beliefs are true (Violate law non-contradiction)
The Flying Spaghetti Monster (incoherent)
I just believe in one less god than you. (Logical fallacy)
When Evidence Conflicts with Knowledge
Sometimes we even know that we should keep believing something is true even if there is much evidence against it.
The story of the guy who knows he's innocent but the evidence against him is overwhelming.
The Biblical Foundation for Knowing Christianity is True
John 14:16-17, 20 - Jesus says the Holy Spirit is with us and gives us assurance that Jesus lives in us and we in him.
Romans 8:15-16 - Paul says we have confidence that we are God's children because his Spirit is in us.
1 John 4:13, 5:6-10 - John says that we have confident knowledge that God lives in us because of the Witness of the Holy Spirit (which is even greater than that of men).
So according to the Bible, we know that Christianity is true because the Holy Spirit lives in us and gives us this Knowledge.
So, how do I know Christianity is true?
You know it's true because the Holy Spirit Witnesses in your heart.
Belief in God as Properly Basic
We have already seen that we have many properly basic beliefs. So why can't beliefs like "God exists" or "Jesus loves me" also be properly basic?
Belief in God is properly basic. Man has an innate, natural capacity to apprehend God's existence even as he has a natural capacity to accept truths of perception (like "I see a tree"). Given the appropriate circumstances—such as moments of guilt, gratitude, or a sense of God's handiwork in nature—man naturally apprehends God's existence. In the same way that certain perceptual beliefs, like "I see a tree," are properly basic given the appropriate circumstances, so belief in God is properly basic in appropriate circumstances.
The Sufficiency of the Holy Spirit's Witness
You don't actually need arguments or evidences at all.
The witness of the Holy Spirit is stronger than any argument.
Most Christians aren't able to study the arguments. So it seems crazy that you can only become a Christian after studying the arguments for years and years!
There is a better way of Knowing Christianity is true - The Holy Spirit
Showing that Christianity is True
We can know it's true by the Witness of the Holy Spirit. But how do we show that it's true?
You show it's true to other people by sharing the arguments and evidence.
The arguments can:
Strengthen your Christian faith, especially when times are bad.
Help you share the faith more bravely.
Be used by the Holy Spirit to help unbelievers come to faith
Help show unbelievers like Muslims that the beliefs they think are properly basic for them (e.g., that Islam is true, etc.) are actually false.