All of Dr. Greg Bahnsen’s articles are reprinted here by the gracious permission of the Covenant Media Foundation

Christians in the ancient world knew what it was to have accusations and ridicule directed at them for their religious convictions and practices. The report of Jesus’s resurrection was taken as an idle tale (Luke 24:11), a lie (Matthew 28:13–15), an impossibility (Acts 26:8). For preaching it, believers were arrested by the Jews (Acts 4:2–3) and mocked by the Greek philosophers (Acts 17:32).

On the day of Pentecost the disciples were accused of being drunk (Acts 2:13). Stephen was accused of opposing previous revelation (Acts 6:11–14). Paul was accused of introducing new gods (Acts 17:18–20). The church was accused of political insurrection (Acts 17:6–7). Experts openly contradicted what the Christians taught (Acts 13:45) and prejudicially vilified their persons (Acts 14:2).

So, on the one hand, the Christian message was a stumbling block to Jews and utter foolishness to Greeks (1 Corinthians 1:23). On the other hand, the early Christians had to guard against the wrong kind of positive acceptance of what they proclaimed. The apostles were confused for gods by advocates of pagan religion (Acts 14:11–13), given unwelcome commendation by soothsayers (Acts 16:16–18), and had their message absorbed by heretical legalists (Acts 15:1, 5).

Twentieth-century believers can sympathize with their brothers in the ancient world. Our Christian faith continues to see the same variety of attempts to oppose and undermine it.

It is the job of apologetics to refute such opposition and to demonstrate the truth of the Christian proclamation and worldview-to “cast down reasonings and every high thing that is exalted against the knowledge of God” (2 Corinthians 10:5).

However, apologetics must not be cooped up in the classroom and academy. It must be taken out into the world of daily life. Christians waste their time if they interact only with academic and hypothetical critics, but not with the man-on-the-street in the flesh.

Not Always Welcome

Like the door-to-door salesman, the believer who takes his apologetic out into the world must expect plenty of rebuffs and antagonism. This is partly because Christianity does not claim to be relatively true (e.g., “It feels good to me, but everybody has his own way of seeing things”). It claims to be absolutely and universally true. Even worse (as far as popular reception goes), Christianity as a religious system claims to be exclusively true. This is quite offensive in a pluralistic, democratic age. “Everybody has a right to believe about God what they wish!” we will be reminded. But that is not the point. The right to believe something does not translate what someone believes into something which is true. The pages of the New Testament show us Christians who responded to the objections and challenges of unbelievers with apologetical arguments for the truth of the faith. The early Christians pressed the claims of truth and were able to defend them, clearly setting the truth of Christ in antithesis to the erroneous ideas which contradicted it. And they did this whether they were formerly fishermen, tax-collectors, or academic students of the law. They “took it to the streets.”

Notice how the New Testament describes the proclamation and defense of Christian faith by its earliest adherents:

Peter proclaimed, Let all the house of Israel therefore know for certain that God has made him [Jesus] both Lord and Messiah (Acts 2:36).
Saul increased the more in strength and confounded the Jews that dwelt at Damascus, proving that Jesus is the Messiah (Acts 9:22).
As his custom was, Paul went into the synagogue, and on three Sabbath days he reasoned with them from the Scriptures (Acts 17:2).
So he reasoned in the synagogue with the Jews and the God-fearing Greeks, as well as in the marketplace day by day with those who happened to be there, [including] certain Epicurean and Stoic philosophers (Acts 17:17).
Every Sabbath he reasoned in the synagogue, trying to persuade Jews and Greeks (Acts 18:4).
Paul entered the synagogue and spoke boldly there for three months, arguing persuasively about the kingdom of God . . . [and later] reasoning daily in the school of Tyrannus (Acts 19:8–9).

When objections are raised to Christianity today, it is likewise our obligation to present reasoned answers in defense. We must argue with those who oppose the truth of God’s Word.

In apologetics our task is to analyze the arguments which are by unbelievers against the truth of Christianity and to produce sound arguments in favor of it. We take our best sanctified ability to reason and debate, using the empirical and logical tools of reasoning which God has granted us, and offer justification for believing Christianity to be true and rejecting the conflicting perspective of unbelievers.

Apologetics is both defensive and offensive in nature; it not only responds to criticism, it also presents its own challenge to the thinking of unbelievers. The defender of the faith must take the battle to the opponents of faith. Apologetics which is both practical and faithful should bring out the irony of the fact that those who demand a defense from God are thereby the ones who in the end stand most in need of philosophical and personal defense.

God has in His holy Word revealed the unholiness of the attitude which presumes that sinners have the intellectual or moral right to call God into question. “You shall not make trial of Jehovah your God” (Deuteronomy 6:16), commanded Moses. When Satan tempted Jesus to do so-to push God into offering proof of the veracity of His Word (as quoted by Satan)-Jesus rebuked Satan, “the accuser,” with these very words from the Old Testament. He declared “It stands written that you shall not make trial of the Lord your God” (Matthew 4:7). It is not God whose integrity and veracity and knowledge is somehow suspect, really. It is that of those who would accuse Him and demand proof to satisfy their own way of thinking or living.

In order for you to “take it to the streets,” like the Christians of the New Testament church did, you need to be able to “cast down reasonings” which are raised up against the knowledge of God (2 Corinthians 10:5)-to very practically and persuasively undermine the beliefs and philosophies held by unbelievers today.

http://www.answersingenesis.org/articles/2009/04/01/where-rubber-hits-road