Pilate receives his wife's note - 'Have nothing to do with this man, for I have been troubled in a dream concerning him' - at the moment when the embodiment of Truth stands before him. Pilate is the embodiment of Reason, and Truth does not reply to Reason's voice. Reason could not believe that God speaks to man through a dream, so he did nothing. The scene is used as the exact picture of what reason does with the Word when it arrives: receives it, cannot credit its channel, and acts on nothing.