In the vestry (or office) to the side of the church, as Tomas realises that he believes life is more understandable without the presence of God, the light through the window behind him intensifies. Assuming the church building has an east-west orientation (as churches tend to do), the light is coming from a northerly direction. Yet, when he later re-enters the church proper (and collapses by the altar rail), the sun is clearly visible, low in the sky, through the window at the opposite (southern) side of the building.