3:15 answer. “Answer” is the Greek apologia, from which we get our word “apologetics,” meaning the careful, logical defense of the Christian faith against the attacks of its adversaries and showing its validity as the true saving gospel of God, our Creator and Savior. In effect, Peter is admonishing believers to be always prepared to give an apologetic for the faith, especially when confronted by those who deny it and would destroy it if they could. This surely means that there is an effective apologetic that can be given, and it is each Christian’s responsibility to study (II Timothy 2:15) and be ready to give it when needed. In contrast, the unbeliever is “without excuse” (Romans 1:20), “without an apologetic.” His faith is strictly based on credulity and wishful thinking, not historical and scientific evidence like that for the Christian faith. On the “defense” (same word) of the gospel, see on Philippians 1:7,17.
3:15 a reason. “Reason” is the Greek logos, from which we derive our word “logical.” We do, indeed, have logical, factual reasons for our hope in Christ (on “hope,” note I Peter 1:3,13,21).
3:15 meekness and fear. Note that our apologetic is to be given not with boasting or pride, but “with meekness and fear” (compare II Timothy 2:24-26). The Christian should not be ignorant in his “answer,” but neither should he be arrogant.