Philip asks Jesus: "Show us the father and it is sufficient for us." Now at this point the disciples had been following Jesus, hearing his teachings, learning from him, yet they did not understand. And we know this because Philip here says Lord show us the father. Philip did not understand even then as Jesus is going to his crucifixion, that Jesus is the father.
I think Jesus’s reply to Philip is the same reply he would give many of us that have been in church all our lives, "have I been with you so long, and yet you have not known me. How can you say show us the father? Do you not believe that I am in the father and the father in me. Believe me that I am in the father and the father in me or else believe me for the sake of the works themselves."