What is the scope of issues that should be included under the field of Christian apologetics? There is the well-known verse, 1 Peter 3:15: “[B]ut 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. . . . .” Based on this passage alone, it might seem that apologetics is mainly limited to the issue of telling unbelievers about individual assurance of salvation (Christ in your heart) and Christ’s resurrection (the basis for “hope”).
But there is more to the story. Paul says that for a man to be qualified to be an elder, he must be “able to give instruction in sound doctrine and also to rebuke those who contradict it” (Titus 1:9). What is the scope of sound doctrine? Jesus says that, “Man shall not live by bread alone, but by every word that comes from the mouth of God” (Matt. 4:4). We also see that the Apostle Paul says, “All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness” (2 Tim. 3:16). The scope of sound doctrine is the entire Bible, and since Paul says to rebuke those who oppose sound doctrine, the scope of apologetics is a defense of the entire Bible. The obligation of the church is to teach all Scripture and defend it against those who oppose it. Theology drives apologetics.
This has implications for the Great Commission. In that speech, Jesus says to “teach them [the nations] everything that I commanded you” (Matt. 28:20a). Everything that Christ commanded includes “every word that proceeds from the mouth of God” – i.e. the whole Bible (cf. Matt. 5:17-20). Therefore, the Great Commission requires us to teach the whole Bible and defend the teachings of the whole Bible. An apologetic that encompasses all the doctrines in Scripture is necessary as part of carrying out the Great Commission.
This does not mean that we should not focus on certain issues with certain groups. It does not mean that an apologetics discussion group cannot focus on defending “the central claims of Christianity.” But we should all keep in mind that defending everything taught in the Bible is the full scope of every Christian’s apologetic obligation. That means apologetics involves addressing issues that divide denominations. Per Titus 1:9, apologetics applies to differences between Christians as well as the differences between Christians and non-Christians. The goal set for the church in the Bible is that “we all attain to the unity of the faith and of the knowledge of the Son of God, to mature manhood” rather than “tossed to and fro by the waves and carried about by every wind of doctrine” (Eph. 4:13,14). For Christ’s church to grow in maturity, it must grow in unity by agreeing about what the Bible teaches in all that the Bible teaches. Spiritual maturity is marked by being able to eat the “solid food” of difficult Bible doctrines, not just the “milk” of “the elementary doctrine of Christ” (Heb. 5:13-6:1; cf. 1 Cor. 3:1-3).
Anybody who has engaged in much apologetic witnessing soon realizes that unbelievers can ask all sorts of questions about the Bible, not just questions about the existence of God and proof of the resurrection. Sometimes they ask about passages in the Bible that few Christians in our day are even aware of, given the shallow preaching and teaching in most of our churches . Being an effective Christian apologist requires a deep knowledge of the whole Bible. Skeptics claim that there are a myriad of contradictions in the Bible. Explaining the resolution to those apparent contradictions requires the Christian to know how different parts of the Bible fit together, especially the details of the Bible’s account of ancient history. One claim is that the story of David killing Goliath is fictional because the text says that David took Goliath’s head to Jerusalem (1 Sam. 17:54); yet, it was not until many years later that David conquered Jerusalem, taking control of the city away from the Jebusites (2 Sam. 5:6-9). A person has to dig into the books of Joshua and Judges to see that, although the Israelites did not control the city until David conquered it as an adult, Israelites lived with the Jebusites in the city before that (Joshua 15:63; Judges 1:21).
How the questions of skeptics are answered often depends on what denominational/theological tradition that a Christian adheres to. Skeptics ask, “Why do Christians condemn behavior based on Old Testament law, yet these same Christians say that eating shellfish is acceptable, even though the Old Testament condemns that too?” There are some Christian theological traditions that will say that all Old Testament law is abolished; others will say that all Old Testament law not repeated in the New Testament is abolished; and yet others will say that all Old Testament law not annulled in the New Testament remains valid. Limiting the scope of apologetics to a few major issues reflects a naïve understanding the questions that skeptics ask and the knowledge required to accurately answer those questions.
1 Peter 3:15/Isaiah 8:13
Last, the understanding of 1 Peter 3:15 presented above is more limited in scope than it should be. As James White recently pointed out in his Dividing Line webcast (here), and as mentioned in some commentaries, Peter derives his statement here from Isaiah 8:13 in the Septuagint version, a Greek translation of the Old Testament often quoted by the New Testament authors. In the English version, Isaiah 8:13 (ESV) reads, “But the LORD of hosts, him you shall honor as holy. Let him be your fear, and let him be your dread.” In comparison, 1 Peter 3:15 (ESV) begins, “But in your hearts honor Christ the Lord as holy.” The parallel is even more obvious in the original Greek. Isaiah 8:13 in the Septuagint begins, “κύριον αὐτὸν ἁγιάσατε.” And 1 Peter 3:15 in the Greek begins, “κύριον δὲ τὸν Χριστὸν ἁγιάσατε.” Peter sticks Christ in the middle of Isaiah’s statement, identifying Christ as the Lord. And since the Greek word κύριον in the Septuagint at Isaiah 8:13 is a translation of the Hebrew word YHWH, Peter is identifying Christ as YHWH, the God of Israel. Although Peter’s words “in your hearts” is not repeating the same words from the Septuagint version of Isaiah 8:13, the thought is the same. To honor Christ as Lord “in your hearts” means the same thing as Isaiah’s command to “fear” and “dread” the Lord.
But seeing that the language of 1 Peter 3:15 is drawn from Isaiah 8:13, we should also see the similar meaning of Isaiah 8:13 in its context to the meaning of 1 Peter 3:15. Seeing the similarity in meaning undermines a narrow view of the subjects to which apologetics properly applies based on 1 Peter 3:15. To honor YHWH as holy per Isaiah 8:13 means to “not to walk in the way of this people” by fearing political conspiracies rather than God’s word (Isa. 8:11). And rather than following the words of fortune-tellers (Isa. 8:19), God’s people should follow God’s word: “To the teaching and to the testimony! If they will not speak according to this word, it is because they have no dawn” (Isa. 8:20). So, Isaiah 8 is teaching that to honor and fear the Lord, people should live their lives in obedience to God’s word, knowing that judgment will come to those who reject God’s word in favor of some other authority.
And if we look at the context of 1 Peter 3, we can see the same thing. Peter is encouraging Christians to obey God’s word in all that they do: “Finally, all of you, have unity of mind, sympathy, brotherly love, a tender heart, and a humble mind” (1 Peter 3:8). The “defense” or “apologetic” that Peter requires in 1 Peter 3:15 is to those who “revile your good behavior in Christ” (1 Peter 3:16). In other words, the apologetic that Peter commands is specifically a defense of living by God’s word as a standard of ethics. That involves defending the existence of God and the resurrection of Christ, but also all of the Bible’s commands to us. As God was allowing Assyria to invade Israel as punishment for Israel’s disobedience to the law of God in Isaiah’s time, the message of the resurrection is not just one of salvation to those who believe in Jesus, but judgment on those who will not live by the standard of the God’s word:
“The times of ignorance God overlooked, but now he commands all people everywhere to repent, because he has fixed a day on which he will judge the world in righteousness by a man whom he has appointed; and of this he has given assurance to all by raising him from the dead.” (Acts 17:30-31).
The word “defense” in 1 Peter 3:15 is the Greek word apologia, from which we get our English word “apologetics.” The Greek word is a combination two other Greek words, apó, meaning “from” and lógos, meaning “intelligent reasoning.” It refers to a reasoned argument in defense of a claim, especially in a court of law. Since the Bible teaches that the resurrected Christ is Judge of the world, the picture presented by Peter in 1 Peter 3:15 is that Christians are Christ’s attorneys, His legal representatives on earth, who are given the task of prosecuting the King’s lawsuit against the unbelievers who have rebelled against the King’s laws.
The idea of a defense in a court of law reflects a common theme in the Old Testament of the covenant lawsuit that God prosecutes against His people when they are unfaithful and against foreign nations when they become exceedingly wicked (see Deut. 28; Ps. 50:7-13; Ps. 83; Isa. 18-20; Isa. 3:13-15; Isa. 41:1-22; Isa. 43:9ff.; Jer. 4-9; Hos. 2:4ff.; Mic. 6:1ff.). Isaiah 8, the very chapter from which Peter draws his command to engage in apologetics in 1 Peter 3:15, is describing a covenant lawsuit against the northern kingdom of Israel coming to its conclusion through the invasion of Assyria to destroy Israel for her sins. These lawsuits make use of the Hebrew word rîḇ, meaning dispute or lawsuit. The Greek word apologeomai, a form of apologia, is used as the translation of rîḇ in a couple of places in the Septuagint (Jer. 12:1, 20:12). The covenant lawsuit is also clearly seen in the book of Revelation, with charges against the seven churches of Asia Minor and later characters like the Beast and the Harlot.
In the Old Testament covenant lawsuits, God offers clemency to the accused if they repent (cf. Jer. 18:8). Of course in the New Testament, King Jesus offers clemency to those who will repent, based on the price of the penalty being paid by the King Himself. Therefore, not only are Christians serving in the role of attorneys prosecuting a case against unbelievers, at the same time “we are ambassadors for Christ, God making his appeal through us. We implore you on behalf of Christ, be reconciled to God” (2 Cor. 5:20). To those who reject the message of reconciliation, however, the message delivered by the Christian serves to further condemn them (2 Peter 2:20-21).
The modern, pietistic view of apologetics as being limited to assurance of personal salvation certainly has no place in 1 Peter 3:15. Merely the fact that Peter calls Jesus YHWH, the God of Moses and the Creator of heaven and earth, should dispel that notion. Regarding the sovereign Creator as holy in your heart has implications as wide as God’s creation. Jesus rules all things, so faith in Jesus has implications for everything in life. His authority extends to all areas of life, whether family, church, science, or politics; therefore, obedience to His word extends to all areas of life. That is what the Christian must defend – all of the Bible in what it says about all of life. That is biblical apologetics. You have “a reason for the hope that lies within you” because you have been saved by Jesus unto good works (Eph. 2:10), rather than living your life in rebellion against God’s word, which eventually ends in judgment carried out by the great God and Savior, Jesus Christ (Titus 2:13), judge of the living and the dead (Rom. 14:9).
 Some who mention the connection are Meyer’s NT Commentary, Barnes’ Notes on the Bible, Pulpit Commentary, and Gill’s Exposition of the Entire Bible: http://biblehub.com/commentaries/1_peter/3-15.htm.
 See Richard M. Davidson, “The Divine Covenant Lawsuit Motif in Canonical Perspective,” https://www.andrews.edu/sem/inministry/uploads/2015fallcoursesyllabi/5.davidson_-_covenant_lawsuit_motif.pdf.
 Kenneth L. Gentry, Jr., “The Seven ‘Letters’ are not Letters” (7/17/2015), http://postmillennialismtoday.com/2015/07/17/the-seven-letters-are-not-letters/.
 An implication of this is that our apologetic methodology must be based on the Bible. See Greg L. Bahnsen, Van Til’s Apologetic: Readings & Analysis (Phillipsburg, NJ: P&R Publishing, 1998), pp. 1-4; Always Ready: Directions for Defending the Faith (Atlanta: GA: American Vision, and Nacogdoches, TX: Covenant Media Press, 1996), p. 63; Presuppositional Apologetics: Stated and Defended (Powder Springs, GA: American Vision Press, and Nacogdoches, TX: Covenant Media Press, 2006), p. 26.