When they saw Him, they worshiped, but some doubted. – Matthew 28:17
Is it possible to worship God and doubt Him at the same time? Well, Jesus’ closest followers did! Of course, at the time of Jesus’ ascension, these men weren’t inhabited by the Holy Spirit (it would be ten more days before that church-forming event would occur); therefore, it is biblically-reasonable to assume that we would have doubted as well. So, you see it is possible to comprehend the glory of God, even to acknowledge it, and yet still doubt His reality.
The disciples could see Him, but perhaps they needed to know that He would never leave them again. They knew the power of the Master, but they were not assured of the presence of the Savior. Jesus undoubtedly perceived all this and spoke to it as only He could. The answer that Jesus gave to all their questions (vv. 18-20) is the same response that He gives to us in our times of doubt.
He wants us to know that He has ALL authority. He has it all. He will never leave us. It is enough.
There lives more faith in honest doubt, believe me, than in half the creeds. – Alfred Lord Tennyson