In a nutshell, the gospel is the good news pertaining to the death, burial, and resurrection of Jesus Christ (I Cor. 15:1-4). Jesus the Messiah, the virgin-born Son of God, lived a sinless life under the Old Testament. Though He did the will of His Father by teaching and working many signs and wonders, He was hated by those who envied Him, and He was brutally crucified for the transgressions of the world. But death could not contain Him. On the third day, He was raised up to walk in newness of life, nevermore to die. To those who believe and obey Him, many wonderful blessings are promised--forgiveness, hope, joy, peace, everlasting life, etc.
Friends, do you see the connection? The gospel appeals to all three parts of man's personality. First, there are facts pertaining to Jesus and the New Covenant that must be believed intellectually. Romans 10:17 says - "So then faith comes by hearing, and hearing by the word of God." Faith cannot exist in a person who has not heard or studied the inspired Scriptures. There is no place in the Bible that teaches that faith is miraculously given by God or His Spirit. The intellectual portion of man's personality must actively receive the gospel message and believe the facts therein.
Second, after the facts are intellectually received and believed, the emotional aspect of man's personality should be stirred. The promises of eternal destruction for the wicked and eternal life for the righteous, as well as sorrow over sin and appreciation for God's love, mercy, and grace, should significantly impact the feelings of the individual.
Third, the intellect and emotions should work together to produce the willpower or motivation to obey the Lord's commands and serve Him to the best of one's ability. II Corinthians 5:14,15 ties these concepts together for us in a beautiful way - "For the love of Christ compels us [willpower], because we judge thus: that if One died for all, then all died [intellect]; and He died for all [emotion], that those who live should live no longer for themselves, but for Him who died for them and rose again [willpower]." The intellect, emotions, and willpower of a person should all be affected in an appropriate response to the gospel message.
It should be noted that the response of each component of man's personality is insufficient without the other two parts. For instance, to intellectually believe the gospel is insufficient without the emotional desire to grieve over sin and yearn for heaven. To emotionally grieve over sin and long for a home in heaven is insufficient without the willpower to obey God fully. The willpower to obey is insufficient without the intellectual knowledge of what should and should not be done.
A beautiful illustration of how the three components of man's personality work together is found in Acts 2. Therein, Peter preached the gospel, which contained facts to be believed by man's intellect (2:22-36). Those who did believe were emotionally stirred--grieved by the terrible wrong they had committed against the Christ. They inquired as to what they should do (2:37). Peter told them to repent and be baptized to have their sins remitted (2:38). He also instructed them regarding living a righteous life and being faithful, which would be impossible without personal willpower and motivation (2:40ff).
Praise be to God for creating us with emotions, intellect, and willpower, and let us rejoice in the fact that the gospel message appeals to all of these aspects of our personality!