Some helpful material I compiled from Van Til, Bahnsen, Anderson, Lisle, and Cheung.
5 but in your hearts honor Christ the Lord as holy, always being prepared to
make a defense to anyone who asks you for a reason for the hope that is in you;
yet do it with gentleness and respect" 1 Peter 3:15
As this verse says "make a defense" that comes from the Geek ἀπολογία which
means to give an argument or reasoned response. Thus as Christians we are to be
ready to give an argument for our faith with Christ at the center of it. Our
argument is to honor Christ's lordship and our actions are to exemplify
likeness of Christ. We are to be gentle and respectful to all who ask of us a
justification of our faith.
"2 that their hearts may be encouraged, being knit together in love, to reach
all the riches of full assurance of understanding and the knowledge of God's
mystery, which is Christ,
3 in whom are hidden all the treasures of wisdom and knowledge." Col 2:2-3
"7 The fear of the LORD is the beginning of knowledge; fools despise wisdom and
instruction." Proverbs 1:7
"1 The fool says in his heart, "There is no God." They are corrupt, they do
abominable deeds, there is none who does good. " Psalm 14:1
"1. That we use the same principle in apologetics that we use in theology: the
self-attesting, self-explanatory Christ of Scripture.
2. That we no longer make an appeal to "common notions" which Chris- tian and
non-Christian agree on, but to the "common ground" which they actually have
because man and his world are what Scripture
says they are.
3. That we appeal to man as man, God's image. We do so only if we set the
non-Christian principle of the rational autonomy of man against the Christian
principle of the dependence of man's knowledge on God's knowledge as revealed
in the person and by the Spirit of Christ.
4. That we claim, therefore, that Christianity alone is reasonable for men to
hold. It is wholly irrational to hold any other position than that of
Christianity. Christianity alone does not slay reason on the altar of "chance."
5. That we argue, therefore, by "presupposition." The Christian, as did
Tertullian, must contest the very principles of his opponent's position. The
only "proof" of the Christian position is that unless its truth is presupposed there is no possibility of "proving" anything at all. The actual state of affairs as preached by Christianity is the necessary foundation of "proof" itself.
6. That we preach with the understanding that the acceptance of the Christ of
Scripture by sinners who, being alienated from God, seek to flee his face, comes
about when the Holy Spirit, in the presence of inescapably clear evidence, opens
their eyes so that they see things as they truly are.
7. That we present the message and evidence for the Christian position as
clearly as possible, knowing that because man is what the Christian says he is,
the non-Christian will be able to under- stand in an intellectual sense the
issues involved. In so doing, we shall, to a large extent, be telling him what
he "already knows" but seeks to suppress. This "reminding" process provides
a fertile ground for the Holy Spirit, who in sovereign grace may grant the
non-Christian repentance so that he may know him who is life eternal. "
An easy apologetics outline: AIM
A- Arbitrariness=Expose the unbelievers assertions that have no justification.
I- Inconsistencies= Expose any inconsistencies in what the unbeliever says.
M- Mistaken foundations for knowledge. One must demonstrate only the Christian worldview can provide the necessary foundations or presuppositions for knowledge. Only from the Christian worldview can one claim to have knowledge (i.e. justified true beliefs) for two reasons:(1) The absolute triune God has revealed truth to us in His Word and continues to illuminate our minds by His Spirit (2) Scripture tells us all mankind are the image bearers of God and hence possess intellects and wills that can reliably acquire knowledge. The goal is to show the unbeliever must assume the Christian viewpoint to know anything with certainty. If any unbeliever claims to have knowledge of anything, he can never be certain since one must either be God or know God to have knowledge of anything. That is because one must be everywhere at once, be outside of time and control everything in order to know something. Since all facts are related to each other. And in order for one to know a fact in its proper context one must know them all.
Unbelievers either reason in a circle putting human reason or experience on the
throne as ruler and ultimate standard of their knowledge. We must show only God
and His Word can rightly be the ultimate standard and authority. Only God can
give us knowledge. Christians, too, argue in a circle. But our circle from God’s
Word provides the necessary foundations/assumptions for knowledge. Moreover, the
circle is rational since the authority appealed to as ultimate is in fact
Ultimate, namely God. Unbelievers are forced into skepticism and/or fideism.
If a Christian gets stumped he can always resort to these questions that can
be phrased in different forms.
“1. Why? A question that demands reasons for whatever is asserted by the
unbeliever so the mistaken foundation can be exposed.
2. So? This question seeks to counter irrelevant things the unbeliever asserts.
3. Really? The question exposes the fact Christianity is the truth and the
unbeliever ought to reexamine his view. But most of all it gives Christians
opportunity to show the unbeliever the necessity of presupposing the Christian
worldview in order to have knowledge.”
 Cornelius Van Til. The Defense of the Faith, 3rd ed. rev. (Nutley, New Jersey: Presbyterian and Reformed Publishing Company, 1967), pp.298-99.
 I made my own acronym from Jason Lisle. The Ultimate Proof Of Creation. (Green Forest: Master Books, 2009),pp.84-95.
 James Anderson via email
 Vincent Cheung. Students in the Real World. http://www.vincentcheung.com/books/invinfaith.pdf p.76.