Jesus told His disciples that if they had known Him, they would have known His Father also. He said from now on they would know the Father and also see Him. Philip replied by asking Jesus to show them the Father and said that would be enough for them. Jesus asked them how was it that He could have been with them for so long yet they still did not know Him. He said that anyone who has seen Him has seen the Father. Therefore, how could they ask to see the Father? He went on to ask them if they believed that He was in the Father and the Father was in Him. He told them that His words came not from His own authority but from the authority of His Father. Jesus challenged His disciples to believe that the Father is in Him and He is in the Father. They should believe this because He was telling them this truth. They should at least believe Him for the sake of the great works and miracles that He did by the power of God.
The point of this section is that Jesus Christ and God the Father are one. If you see Jesus you see the Father. We see this truth proclaimed in the Old Testament prophecy of the coming Child and Son who would be born and who would be God the Father.
For unto us a Child is born, Unto us a Son is given; And the government will be upon His shoulder. And His name will be called Wonderful, Counselor, Mighty God, Everlasting Father, Prince of Peace. Of the increase of His government and peace there will be no end… (Isa. 9:6-7)