The Christian should be ready with a defense concerning the Truth that is in us (1 Peter 3:15). We should be ready to defend the honor and glory of our God. We should know what we believe and why we believe it.
You can be assured that the atheists will have questions for which they assume we have no answers. We should be prepared to prove them wrong.
We are to ‘contend earnestly’ for the truth of the Gospel of Jesus Christ. We must make sure that the facts concerning who He is, what He has done, and what He is currently doing, are understood correctly. Knowing these facts and responding to them in faith will bring a person into a saving relationship with Jesus Christ.
It is trust in Christ that cleanses us from sin and renders us forgiven in God’s eyes. It is not belief in one particular personal pet doctrine or another. The goal of the Christian life is holy living, living according to God’s will for ones life so that our lives will be witnesses to others of the love of God.
However, if the Christian thinks that living according to God’s will hinges on any debatable non-essential doctrine to which they subscribe, then their focus is not enough on Jesus. If any doctrine gives cause or license to sin, one needs to abandon or rethink that doctrine. Salvation is accomplished by the life, death, burial, and resurrection of Jesus Christ and our response to that knowledge.
In addition, one should not be so arrogant as to think that someone else is not saved because they do not hold to exactly the same beliefs on peripheral issues. It is not biblical to say that someone can trust Christ for salvation but not be saved because they have a misunderstanding, or no understanding, of a particular peripheral issue.
Let us carefully evaluate what the Bible says is essential for salvation and living the Christian life, and what is not essential. We can discuss the non-essentials, even debate them, but they should not cause division amongst Christians.
On the other hand, we should whole-heartedly contend for the true faith against those who, like the troublemakers in Jude, would seek to do harm to the body of Christ…the church.