Before getting into this topic, we have to establish what the following verses have in common. I’ve chosen a number of verses from throughout the New Testament. Let’s take a look at them.
For the Law was given through Moses; grace and truth came through Jesus Christ.
Now in the Law Moses commanded us to stone such women. So what do You say?
…for all have sinned and fall short of the glory of God, and are justified by His grace as a gift, through the redemption that is in Christ Jesus…
Now the Law came in to increase the trespass, but where sin increased, grace abounded all the more…
For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord.
All of the above verses, as you may have noticed, draw a distinction between the Law, on the one hand, and the Gospel, on the other hand. The Law tells us what God commands; the Gospel tells us what God promises. The Law says, “Do this and live;” the Gospel says, “Christ died for all, that those who live might no longer live for themselves but for Him who for their sake died and was raised,” and “If we live by the Spirit, let us also walk by the Spirit.” Reformed minister in the Church of Scotland, John Colquhoun summarizes the Biblical Law/Gospel distinction in this way:
The Law…promises eternal life to man on condition of his own perfect obedience, and of the obedience of no other; whereas [the Gospel] promises it on condition of the perfect obedience of Christ received by faith, and that of no other. The promise of Law as a covenant is the promise of God as an absolute God; but the promise of the Gospel is the promise of God as a God of grace in Christ. The promise of the former was to have been performed after obedience, whereas the promise of the latter begins to be performed to the true believer before, and in order to, his obedience. In the Law of works the promise of privilege is grounded upon the performance of duty; but in the Gospel the performance of duty is founded on the promise, and even the enjoyment, of privilege. The promise of the Law is strictly conditional, but the leading promises of the Gospel are, to us, entirely absolute.
This distinction is important to the whole of the Christian faith, as it concisely describes the two ways in which man relates to God. A man is either under the Law, or he is under grace; there is no middle ground. A man is either the recipient of God’s wrath or the recipient of His grace. A man is either condemned by the Law, or he is justified by the Gospel. To those who are proud in heart, we preach the Law to show them their sin, “so that every mouth may be stopped, and the whole world be held accountable to God. For by works of the Law no flesh shall be justified in His sight, since through the Law comes knowledge of sin.” To those who are laden with guilt, upon whose hearts the weight of their rebellion against God continually rests, to these Christ says: “I will give you rest…and you will find rest for your souls.”
What Does this Distinction Have to Do with Apologetics?
“Apologetics is the branch of Christianity that deals with the defense and establishment of the Christian faith.” As such, it is concerned with providing answers to common objections to the Christian faith, which are, in essence, objections to the revealed character and will of God. To object to the revealed character of God is to object to God Himself; and to object to the revealed will of God is to object to His standard of moral judgment; it is, therefore, to sin. On the other hand, apologetics aims to provide not only a critique of non-Christian worldviews, but also seeks to establish the Christian faith. These two ways of doing apologetics have been called negative apologetics and positive apologetics. In my own estimation, negative apologetics, which seeks to dismantle supposed opposition to the Christian faith, corresponds roughly to the Law, the primary purpose of which is to remove the unbeliever’s supposed grounds for continuing in sin; whereas positive apologetics, which presents proofs in favor of the Christian faith, corresponds roughly to the Gospel. The former exposes the heart of Christ’s opponents in revealing their underlying presuppositions and removing the possibility of making excuses for themselves; the latter is declarative, presenting the Christian faith to the unbeliever in purely positive terms. Here are some texts that will, I hope, show you what I mean.
|[a.] “Negative” Apologetics (Law)||[b.] “Positive” Apologetics (Gospel)|
|We destroy arguments and every lofty opinion raised against the knowledge of God, and take every thought captive to obey Christ…
We must be able to refute those who are in error
God has destroyed the wisdom of the wise
|But in our hearts we honor the Lord as holy, always being prepared to make a defense to anyone who asks us for a reason for the hope that is in us…
But we must hold firm to the trustworthy Word [of the Gospel] as taught, and give instruction therein…
But Christ has become for us wisdom from God
In column [a.], the task is one of deconstruction, destroying opposing worldviews; in column [b.], the task is one of building up, making a defense. Again, in column [a.] the task corresponds to the preaching of the Law in that it removes any supposed excuse an unbeliever may present for his unbelief; in column [b.], the task corresponds to the Gospel in that it presents a positive case for the Christian faith. The former leaves the proud unbeliever without excuse, removing all pretence, and exposing the nature of his unbelief (it is moral first and intellectual second); the latter gives the unbeliever what he cannot on his own find and possess: the truth.
Understanding the rough correlation between Negative/Positive Apologetics and Law/Gospel Distinction, I think, may be helpful in guiding our interactions with non-Christians. There is a time for negative/deconstructive/destructive apologetics; and there is a time for positive/constructive apologetics. The question of which methodology would be best to use depends on the situation at hand. As the Law is for the proud and the Gospel is for those humbled by God’s convicting Word by the power of the Holy Spirit, so negative apologetics, for me, has usually been most helpful in dealing with those who think that they have strong, rock-solid anti-Christian arguments, while positive apologetics has been helpful in dealing with those who have seen the fragility of all thought systems and religions that stand in opposition to Christianity. In either case, we are called to earnestly contend for the faith once for all delivered to the saints, so may the Lord grant us the discernment needed to effectively use both of these methods of argumentation.
 John 1:17
 John 8:5
 Ro 3:23-24
 Ro 5:20
 Ro 6:23
 2 Cor 5:15
 A Treatise on the Law and the Gospel, pp. 149-150 (Soli Deo Gloria Publications, 2009)
 Ro 3:19-20
 Cf. Matt 11:28-30
 Cf. 2 Cor 10:5
 Cf. Titus 1:9b; There are two issues with this citation that need to be addressed here, namely: (i.)Within the context of Titus, Paul is describing what qualifications an elder must have in order to serve; however, I believe that this qualification is a sub-qualification of always being ready to give a defense. The difference, then, would be one of degrees to which the task could be carried out. The elder is held to a much degree of responsibility for taking of God’s people and keeping them from going astray (cf. Eph 4:11-16 & James 3:1); and (ii.)The command to refute those in error is applicable to all opponents of Christianity who, by dint of proposing a worldview that denies the Christian faith, are contradicting the truth.
 Cf. 1 Cor 1:18-21
 1 Peter 3:15
 Cf. Titus 1:9a
 Cf. 1 Cor 1:30