When Jonas sees the newborn twin’s release, it makes him realize his community cannot go on the way it has been and he must do something about it.
Jonas has lived all of his life believing that his community is harmless. Once he begins his training, he still thinks that although the people have no real opportunity to feel, they still are not really doing harm. He understands that they simply do not have real emotions.
When Lily describes herself as feeling anger during the traditional telling of feelings, Jonas understands that it is not really anger that she is feeling. No one in the community actually feels genuine anger.
But Lily had not felt anger, Jonas realized now. Shallow impatience and exasperation, that was all Lily had felt. He knew that with certainty because now he knew what anger was. (Ch. 17)
The community has done away with real emotions, so Lily has never felt one. His parents have never felt them. Jonas has experienced them though, in the memories. He understands that his community controls them through the Stirrings pills and that is why he refuses to take them.
What Jonas does not completely comprehend is the true meaning of release. He still thinks that although his people can’t feel love, or hate, or anything really, that does not make them dangerous. When he sees his father murder an innocent newborn baby for essentially no reason, and with no remorse or any emotion at all, he is completely shocked.
Jonas’s first reaction is horror that his father could so callously kill a baby, and his second one is resentment that his entire community is mindlessly cruel.
Jonas mimicked in a cruel, sarcastic voice. "I will do whatever you like, sir. I will kill people, sir. Old people? Small newborn people? I'd be happy to kill them, sir. Thank you for your instructions, sir. How may I help y--', He couldn't seem to stop. (Ch. 20)
From here on, Jonas cannot accept the way things are. He refuses to acknowledge that a society where emotions are not allowed is one where the people are free. Killing babies is Jonas’s last straw. He wants to know how he can change this, and The Giver and Jonas devise a plan to free the community from its bonds. Jonas will escape with The Giver’s help. They will return the memories to the people, and thereby teach them to feel—force them to feel.
Jonas’s plans are cut short when he learns that Gabriel, a toddler he has bonded with who is living in his home, is scheduled for release. Jonas escapes early, alone, without The Giver’s help. They still return the memories, but the trip is much more dangerous, and the two risk death if they are captured, and almost die during the journey.
In the shocking scene when Jonas watches his father murder the newborn twin, the reader learns alongside Jonas how tragic things really are in Jonas’s community. Up until this point, information about the community is controlled for the reader as well as for Jonas.
In this chilling climax, Jonas has to make an emotional choice. His world is shattered as he realizes what has really been going on all around him all of his life, and the reader does too. Particularly tragic for Jonas is the fact that his father is the one doing the killing, and he learns that Fiona, his close friend and a girl he is coming to like, is already learning to kill the elderly. Any emotional connection Jonas has to his community's ways is melted in that realization.