It is easy to try to “out-reason” or “out-argue” unbelievers with the Gospel truths.  Yet, such an approach to people who are spiritually blind and morally enslaved will be futile in our own strength.  The following is an application Friedrich Krummacher makes from 2 Samuel 5 to our interactions with the unbeliever.

The words of the Lord, “When thou hearest the sound of a going in the tops of the mulberry trees then thou shalt bestir thyself,” are important for us also, in a figurative sense, in our warfare with the children of unbelief in this world.  They teach us that in our own strength, and merely with the human weapons of reason and science, we are not to make war against the adversary.  Success an only be counted upon when the conflict is undertaken under the influence of the Holy Spirit of God, breathed forth and in the immediate blessed experience of the gracious presence of the Lord, and of the truth of His Word. Then there breaks forth from our hearts that which we call “testimony” – a speaking from the present enjoyment of salvation, a speaking arising from a comprehensive, vital, powerful conception of the infallibility of that for which the undertaking has been begun; a speaking of the whole animated personality.  This breaks through the enemy.  No bulwark of science, falsely so called, withstands this. (Friedrich Krummacher, David: King of Israel, page 220)

This is the biblical approach to apologetics, not ceding turf to the unbeliever nor “reasoning” on his foolish terms, but through the Holy Spirit’s testimony in the Word and in our heart – the immediate blessed experience of the gracious presence of the Lord – launching an unstoppable assault on the very heart of the individual calling their rebellion out and commanding repentance and faith before the Lord.