The united, unequivocal witness of the New Testament is that Jesus rose from the dead. That conviction permeates gospels and epistles, it drives the apostolic mission forward, and it underpins the looking forward to the End of all things in Revelation.
But what gave rise to that conviction? If we focus on Paul then we have an example of someone in our situation: he had not (as far as we know) met Jesus in his wanderings, but he had engaged with Christians who believed that Jesus rose from the dead, and he encountered the risen Jesus in an experience which, though more 'spectacular' than most of us testify to, was nevertheless an experience of Jesus after the point in time when any claims were being made that he was appearing routinely in the first days and weeks after his resurrection in earthbound ways (e.g. eating, drinking, meeting with people).
One question biblical scholars have asked, noting Paul's presence in the chain of appearances in 1 Corinthians 15:6-8, is whether there was a difference between Paul's experience at the (we could say) post-Ascension end of this chain and the pre-Ascension experiences of Cephas at the beginning of the chain. This is a tricky (if not, trick) question. Answer 'yes' and the next question follows: how is the difference to be described? Your answers in the comments would be welcomed ... but don't worry if you start and give up! Answer 'no' and some scholars pounce, "Ah, you see, there is no necessary link between the empty tomb narratives and the appearance narratives. In fact, could we not say that the empty tomb narratives are rather clever stories invented by the gospel writers to provide a semblance of an objective 'event' based support for the subjective events of experiencing the risen Jesus through his appearances?"
To go back to the beginning of this post: one difficulty with working through the many critical questions raised about aspects of the resurrection narratives is that a forest of trees grow up which prevent the wood being seen.
Whether the gospel narratives are recounted, or the epistles reread, the unmistakeable conviction of the New Testament writers is that Jesus rose from the dead.
This conviction, I suggest, goes beyond 'a few followers of Jesus saw appearances of Jesus and convinced others that he had risen from the dead' or 'after a period of despair and sorrow the disciples began to feel differently about things, hope sprang to life in their human hearts and they began to think this meant that Jesus was not dead but lived on in their midst.'
It was a conviction that Jesus as the person Jesus, not as a ghostly appearance resembling the pre-crucified Jesus and not as a feeling in their hearts that life was on the up, was no longer dead. He had risen from the dead, escaped the shackles of death, fought and beaten the last enemy death. Jesus was alive. "I died, and behold I am alive forevermore, and I have the keys of Death and Hades" (Rev. 1:18). This conviction was certainly consistent with the testimonies in the gospels to the empty tomb, to meetings with Jesus in everyday situations including a barbie on the beach (John 21), and to his ascending visibly to the Father (Acts 1). But the conviction goes beyond experiences of Jesus being alive after death (so that, for instance, his resurrection was on a par with Lazarus') to a conviction that he would be 'alive forevermore' and that he had power or 'the keys' over 'Death and Hades.'
So the tomb was empty and that helped with the conviction that Jesus was raised from the dead; but the conviction was driven along by other forces at work in the Christian community, and it continues to be driven along by those forces: the Holy Spirit and the Word of God expressed through reading and teaching the Scriptures.