The eleven disciples went to Galilee,
to the mountain to which Jesus had ordered them.
When they saw him, they worshiped, but they doubted.
Then Jesus approached and said to them,
"All power in heaven and on earth has been given to me.
Go, therefore, and make disciples of all nations,
baptizing them in the name of the Father,
and of the Son, and of the Holy Spirit,
teaching them to observe all that I have commanded you.
And behold, I am with you always, until the end of the age."

Matthew 28:16-20

What catches the eye in this story is that, in the very process of worshiping the risen Jesus, the author notes, “but they doubted.”  This occurs just three verses before the end of the entire Gospel!  It was immediately prefaced with a believable alternate explanation of the Resurrection: Matthew says the chief priests encouraged the guards to tell the people Jesus’s body was stolen by his disciples, “and that this story has been spread among the Jews to this day.” (Matthew 28:11-15)

The theme of doubt around the Resurrection appears in all four Gospels:

In the Gospel of Mark, Mary Magdalene’s story of encountering the risen Jesus, reported to the apostles, is dismissed: “they would not believe it.” (Mark 16:11) When he appears on the road to two disciples and they tell the apostles, again Mark records, “but they did not believe them.”  (Mark 16:13) Jesus finally appears to all eleven apostles and, “he upbraided them for their unbelief,” even as he commissions them to spread the Gospel throughout the world. (Mark 16:14)

In Luke, Mary Magdalene’s story is corroborated by two other women but receives even less respect: “but these words seemed to them as an idle tale and they did not believe them.” (Luke 24:11) The story of the two disciples appears in Luke as well, and Jesus criticizes the two harshly for not recognizing him: “O foolish men and slow of heart to believe all that the prophets have spoken!” (Luke 24:25).  When Jesus appears to the apostles, he has to show them the nail wounds in his hands and feet and they, “still disbelieved for joy.” (Luke 24:41) 

In the Gospel of John, disbelief is concentrated and personified exclusively in Doubting Thomas who demands to see Jesus’s wounds and is scolded for requiring proof. (John 20:26-29)

What are the authors of Scripture trying to convey by this?  One explanation is that the Gospels writers are inviting us to look deeper.  The Resurrection story is not supposed to be a proof of God’s existence – you don’t use an account as proof if the eyewitnesses themselves remain skeptical and even offer an alternate explanation. God’s existence is treated as a given in each of these narratives.  No, the Resurrection is intended to assert something else.