The Confirmation students talked about if we can trust the New Testament eye witnesses. If the writers of the New Testament were liars, many could refute the claims at the time of speaking and writing. They would also be giving up their lives for a lie. Seems like they were pretty certain in what they say and believed.
“Now Jesus did many other signs in the presence of the disciples, which are not written in this book; but these are written so that you may believe that Jesus is the Christ, the Son of God, and that by believing you may have life in his name.” -John 20:30-31