Through a Glass Darkly

The story takes place during a twenty-four-hour period while four family members take their vacation on a remote island, shortly after one of them, Karin (Harriet Andersson), is released from an asylum where she has been treated for schizophrenia. Karin's husband Martin (Max von Sydow) tells her father, David, that Karin's disease is almost incurable. Meanwhile, Minus (Lars PassgÃ¥rd), Karin's 17-year-old brother, tells Karin that he wishes he could have a real conversation with his father and cries because he feels deprived of his father's affection. David (Gunnar BjÃ¶rnstrand) is a novelist suffering from "writer's block" who has just returned from a long trip abroad. He announces he will leave again in a month, though he promised he would stay. The others are upset and David gives them unthoughtful, last-minute presents. He leaves them and sobs alone for a moment. When he returns, the others cheerfully announce that they too have a "surprise" for David; they perform a play for him that Minus has written. David, while feigning approval of the play, takes offense since the play can be interpreted as an attack on his character.
That night, after rejecting Martinâs erotic overtures, Karin wakes up and follows the sound of a foghorn to the attic. She faints after an episode in which she hears voices behind the peeling wallpaper. David, meanwhile, has stayed up all night working on his manuscript. Karin enters his room and tells him she can't sleep, and David tucks her in. Minus asks David to come with him out of the house, and David leaves. Karin looks through David's desk and finds his diary, learning that her disease is incurable and that her father has a callous hunger to record the details of her deterioration.
The following morning, David and Martin, while fishing, confront each other over Karin. Martin accuses David of sacrificing his daughter for his art and of being a self-absorbed, callous, cowardly phony. David is evasive but admits that much of what Martin says is true. David says that he recently tried to kill himself by driving over a cliff but was saved by a faulty transmission. He says that after that, he discovered that he loves Karin, Minus and Martin, and this gives him hope.
Meanwhile, Karin tells Minus about her episodes, and that she is waiting for God to appear behind the wallpaper in the attic. Minus is somewhat sexually frustrated, and Karin teases him, even more so after she discovers that he hides a men's magazine. Later, on the beach, when Karin sees that a storm is coming, she runs into a wrecked ship and huddles in fear. Minus goes to her and she grabs him. Though the act is not shown, the film suggests that Karin has sexually seduced her brother.
Minus tells the other men about the incident in the ship and Martin calls for an ambulance. Karin asks to speak with her father alone. She confesses her misconduct toward Martin and Minus, saying that a voice told her to act that way and also to search David's desk. She tells David she would like to remain at the hospital, because she cannot go back and forth between two realities but must choose one. While they are packing to go to the hospital, she runs to the attic where Martin and David observe her actions. She says that God is about to walk out of the closet door, and asks her husband to allow her to enjoy the moment. She becomes fixated on a crack in the wall out of which emerges a spider. The ambulance, a helicopter, flies by the window, making a lot of noise and shaking the door open. Karin moves toward the door eagerly but then she runs from it, terrified, and goes into a frenzy of panic. Karin vanishes and, reappearing in a frenzy, is sedated. When she stands, she tells them of God: an evil-faced spider who tried to penetrate her. She looked into God's eyes, and they were "cold and calm," and when God failed to penetrate her he retreated onto the wall. "I have seen God," she announces.
Karin and Martin leave in the helicopter. Minus tells his father that he is afraid, because when Karin had grabbed him in the ship, he began leaving ordinary reality. He asks his father if he can survive that way. David tells him he can if he has "something to hold on to." He tells Minus of his own hope: love. David and his son discuss the concept of love as it relates to God, and the factor of human father-child relationships in the perception of God, in the stretching final chapter of the film. Minus seems relieved and is tearfully happy that he finally had a real conversation with his father: the film ends with his line, "Papa spoke to me."

Question: What is David's own hope that he holds on to?
Answer: Love