John 14:8 - Albert Barnes' Notes on the Bible

Lord, show us the Father - Philip here referred to some outward and visible manifestation of God. God had manifested himself in various ways to the prophets and saints of old, and Philip affirmed that if some such manifestation should be made to them they would be satisfied. It was right to desire evidence that Jesus was the Messiah, but such evidence “had been” afforded abundantly in the miracles and teaching of Jesus, and that “should” have sufficed them.