In Acts 17:30-31, Paul says, "The times of ignorance God overlooked, but now he commands all people everywhere to repent, because he has fixed a day on which he will judge the world in righteousness by a man whom he has appointed; and of this he has given assurance to all by raising him from the dead." This message by John Piper is far and away the greatest explanation we have encountered regarding how people are assured of the final judgment by the certainty of Christ's historical resurrection. The answer may surprise you.
According to Paul's statement in Acts 17, the main evidence of the final judgment of men by Jesus Christ is the undeniable proof found in the reports of Jesus' resurrection, together with the Bible's teaching about its meaning. When the resurrection of Christ is preached, together with its biblical significance, all men, everywhere, even philosophers in Athens who knew nothing about the Jewish Messiah until Paul showed up evangelizing, are furnished with enough assurance from God of the final judgment at the throne of Christ to be without excuse. This means that the biblical accounts of the resurrection carry with them undeniable proof for its historicity, and that God's Holy Spirit convicts men of this truth, so as to leave them without excuse. Therefore both the faithful preaching of the gospel and the biblical evidences for the gospel carry their own sufficient credentials and leave hearers without excuse. That is, in God's mind (and he is the perfect judge who knows the secret thoughts of men) both Gospel preaching and the biblical accounts and witnesses to Christ's resurrection are self-attesting and undeniably so. As demonstrated in Acts 17, Paul believes God provides all people with enough warning of the end time judgment of Christ by testifying to them about the resurrection of Christ (even if that preaching is indirect, coming from second- and even third-hand sources), meaning unbelievers do not have to be eye-witnesses to the resurrection in order to have received undeniable proof of its truth. The Gospel accounts are self-attesting.
In other words, God holds men accountable for having been warned of judgment, precisely because the argument He uses to prove this judgment's certainty is in God's mind more than sufficient. God has assured the world, convincingly, that he will judge the world by a man. He proves this by the plain and undeniably true proclamation of the resurrection of Christ. We highly recommend this message! Anyone who regularly preaches the gospel to others, especially to those hostile to its historical claims, ought to familiarize themselves with the argument and logic of this message. Those who often find themselves defending the faith would be wise to master the basic argument for themselves. The message also sheds much light on the importance of the resurrection for gospel preaching, and it offers insights into how the apostles preached the doctrine.