One of the clearest explanations of the Gospel is found in the first letter of John, chapter 5, verses 6-13. God himself has born witness to Jesus as his only Son. Those who believe in Jesus have the testimony in their hearts. Those who do not believe make God a liar! And THIS is the testimony: “God gave us eternal life and this life is in his Son.” Here it is a plain as plain can be: “Whoever has the Son has life. Whoever does not have the Son of God does not have life.” Then John says, “I write these things to you that believe so that you may KNOW that you have eternal life.”
For the peson who believes the testimony of God regarding Jesus it is not a matter of wishful thinking. Nor is it a matter of betting on the odds. It is a matter of God’s word and the truth. Those who believe will inherit eternal life. Those who do not will not. Even a child can understand that. Interesting enough, it is not children who doubt. It is adults who acquire complicated arguments and patterns of life that exclude God’s word and then question its truth. 1 John states the truth without exception the same way Luke says it in Acts 4:12. “There is no other name given among men whereby we might be saved.” This is the Gospel, simple and sweet!