The gospel, of course, embraces all the truths concerning the person and work of Jesus Christ, from creation to consummation. Since these truths have been under Satanic attack throughout all the ages, it is vital that the gospel both be defended against its enemies and confirmed in the hearts and minds of its friends.
The word for "defense" (Greek, apologia) is the same as "answer" in 1 Peter 3:15 where we are commanded to "be ready always to give an answer . . . a reason of the hope that is in you." The word for "confirmation," on the other hand, is essentially the same as "established," or "stabilized," as in Colossians 2:7: "Rooted and built up in him, and stablished in the faith." Thus the saving gospel of Christ--from its foundation in genuine creationism to its consummation in His coming kingdom with its central focus on the crucifixion and resurrection--is both to be defended against false teaching and established as truth. These two aspects correspond in general to apologetics in defending the faith and Christian evidences in establishing the faith.
This is not merely a job for certain theological or scientific specialists, however. All believers need to be "partakers" of this grace (literally "convinced co-participants"). Real "partakers" do not just go along for the ride, but are firmly committed and fully comprehending supporters. However, both those who lead out in such a work, as well as those who are "partakers," are exhorted to do so in grace! "Let your speech be always with grace, seasoned with salt, that ye may know how ye ought to answer every man" (Colossians 4:6). HMM http://www.icr.org/articles/type/6/