"Wherefore let him that thinketh he standeth take heed lest he fall" (1 Cor. 10:12, KJV).
"Wherefore the rather, brethren, give diligence to make your calling and election sure: for if you do these things you shall never fall" (2 Pet. 1:10, KJV).
"But he that shall endure to the end, the same shall be saved" (Matt. 24:13; cf. 10:22, KJV).
We aren't born
tabula rasa, which John Locke believed, with a blank slate but are naturally creatures of faith as a sixth sense or instinct and that is the primary way we first learn: we take our parent's word for it! Faith is knowledge acted upon and
knowledge used wisely is wisdom. Both are virtues we should practice as believers. The definition of knowledge is believed or interpreted as being a
justified true belief--we must believe it and it must be for a good reason, as if by some authority.
Faith is putting trust in what we have good reason to believe. It's also knowledge in action. We have a right to our own
opinions about the knowledge we know but cannot make up our own knowledge or fabricate our own truths.
Beliefs can be true or false and are very subjective, while truth itself is what corresponds with reality according to the
correspondence theory of truth of John Locke. To Christians, truth is what agrees with God. Nothing is true because it's believed or untrue because it's doubted.
Children may learn to believe in Santa (a harmless myth) by being encouraged and they will eventually find out it's all pretend, but they usually know we are serious when we relate the true Christmas story. We can all learn lessons of childlike faith and innocence from kids (cf. Mark 10:45). They need to learn faith and put it into practice! Parents don't destroy the children's faith in Santa, they just outgrow it by being around older and more mature kids or from the real world. Kids have a big imagination and would probably believe even if not so encouraged.
Many atheists will insist they were once believers who lost their faith (the Bible would call this going apostate and departing from the faith which only proved they never had any according to 1 John 2:19). They had some traumatic experience they couldn't cope with and took it out on God, developing an animus towards Him and then towards Christians, becoming
militant atheists even anti-theists bent on destroying the influence of the church and neutralizing Christian influence.
It should be noted that the same sun melts the butter, hardens the clay; we all either become
bitter or better by the same experience and no one skates through life trouble-free without adversity or trials. Our faith must be tested in the crucible of the trench warfare of real OJT in life. Even Jesus didn't exempt Himself from adversity and was honest enough to warn us and to count the cost of discipleship.
You don't need all the answers to believe and just because you believe it doesn't mean you can defend your faith, But
belief without evidence is called blind faith and we are commanded to have a reason for the hope that is in us! Being apologists is for all believers! We are to "contend for the faith" (cf. Jude 3) and "in defense of the gospel"(cf. Phil. 1:7) as Jude and Paul did respectively.
We must remember that no matter how strong our faith, it's still
faith and we are saved by faith, not knowledge, which is the error of Gnostics who try to achieve a secret, privileged knowledge of the elite. We are not saved by
intellectualism either--it isn't how much we know, but Whom we know as Paul said in 2 Tim. 1:12 that
"I know in whom I have believed...." Christianity isn't a faith of
enlightenment, but of salvation and redemption from the real culprit-
sin, not ignorance. Assurance is not an automatic fruit of salvation but belongs to its well-being, not being and some people need to have a spiritual wake-up call before realizing their precarious faith.
One warning Jesus gave was not to cause a brother
to stumble (cf. 1 Cor. 8:12) or a child to lose faith! To wage war against the saints is odious to God. We're all supposed to be on the same side as they say in the battle to the troops fighting each other; "The enemy is over there!" Note that it's been said that we are our own worst enemies! We should be fighting sin and evil, not each other! We ought to maintain the unity of the Spirit in the bond of peace per Eph. 4:3. It's our job to reassure and foster faith in the weaker brother, but it's not our calling to certify salvation.
Now faith is the "substance of things hoped for and the evidence of things not seen" according to Hebrews 11:1. For illustration purposes, let's say I reach my hand into my pocket and grab something and ask you what it is! I hold it behind my back and you take a guess or two. Finally, you come to believe I'm holding my car keys because you can hear them! That's right,
there's evidence for faith! But this is still faith though you are convinced. But let's say I open my hand and show you my keys in them; then
I've destroyed your faith and given you
first-hand knowledge!
This is akin to getting the first-hand knowledge of our Lord and Savior via a personal relationship with Him--we have encountered Him empirically and know Him like for who He is and what it says: "Taste and see that the LORD is good" (cf. Psalm 34:8). The
proof of the pudding we'll find out is in the eating! We need believers with first-hand experience and knowledge of the Lord. But know this: It's faith till we eat! What I'm trying to say is that we can know God and be sure of our salvation by the Spirit residing in us: "The Spirit bears witness with our spirit that we are sons of God" (cf. Romans 8:16).
Let's take another example of faith: a tightrope walker demonstrates he can walk across the rope with a wheelbarrow and asks how many actually believe he can push a person across in it! Almost everyone raises their hands and says they believe. Then he asks of a volunteer! No one is willing to test their faith! Where's the faith now? He didn't kill their faith but found out they had none for we must be willing to
exercise or put it into practice for it to be
bona fide, saving faith. Anyone can say they have faith but it must be proved by our behavior, conduct, and works--we're known by our fruits per Matt. 7:20.
A good example of faith in action is a kid flying a kite on a cloudy day: The passerby asks him how he knows the kite is really up there since he doesn't see it! The kid says, oh, I feel a tug every now and then to reassure me. Likewise, we feel God drawing us towards Him in fellowship and love. Faith is like that--God reassures us and keeps us in the faith and doesn't let go. Experience in flying kites made his faith strong and likewise, an experienced walk with Christ yields strong faith. The more trials we successfully pass with flying colors the more real our faith to us.
NB: Our faith is held by God's power (cf 1 Pet. 1:5) who will not let go of us nor give up on us (cf Phil. 1:6)--we're all works in progress. Someone hostile to the faith may ask some questions we cannot answer, but no issue or problem with the Bible or the faith is going to bring Christianity to its demise after 2,000 years. But sometimes God allows us to have doubts and to experience hardened hearts; it is important to realize that doubt is not a Christian problem but a human one, it's an element of faith, not the opposite of it. It can take courage to doubt.
But in the final analysis, we should doubt our doubts and believe our tried and true faith, so we can say with Paul's swan song (cf. 2 Tim. 4:7): "I have fought the good fight, I have finished the race, I have kept the faith," knowing we are kept in Christ from beginning to end (cf Jude 1: 24). God doesn't teach us to swim only to let us drown!
In sum, let me quote the late Rev. Billy Graham: "If you want to keep your faith, you must give it away!" Let me add: A privatized faith is no more than a cloistered faith that cannot reach out to the lost. Soli Deo Gloria!