Lewis is a very deep intellectual thinker who understands life and tries to meditate on different aspects in life. This specific example takes place in a tool shed where he is looking at a light beam and all the dust particles that are floating around, and then walks into the light beam and stares directly up into the sun. He then contrasts this event and takes it into many points of view in life.
He gives an example of a man in love, and now that he is in love, he see's the world from an entirely different angle just as he was while looking up at the beam of light. With the girl, the man is a totally different person and see's life very differently. Later in the story Lewis brings up an example of pain. He states that one cannot know what pain is unless he has suffered through pain at some point in his or her life. So he concludes that one must experience pain both through seeing it and by having pain.
Religion can be fit in by both seeing and believing. When one see's a person filled with the spirit, they must recognize what it is and then believe. It is about looking at religion from different angles, as is the point of the entire essay.