Even after the final page of On the Beach, it may take us a while to grasp the fact that all the characters in the book have committed suicide, the ultimate act of self-destruction. Before the radiation even comes down to kill them, many of the characters are actively seeking out other ways to kill themselves. Moira drinks herself to oblivion, as does Douglas Froude, against his doctor's orders. John tries his best to finish himself off racing in his Ferrari.
Some characters, however, do their best to preserve life, but often do so in a delusional mindset. Mary reacts hysterically to Peter's instructions on euthanizing Jennifer because it is against all instinct for a mother to kill her own child. A mother's role is to create and preserve the next generation, not destroy it. Shute wants to prove that nuclear war is humanity's ultimate act of self-destruction. There is no winner in a nuclear war; even the last survivors get only the prospect of a dignified, self-administered death by pills as their prize. The message is especially meant for those in nations—such as Australia—who like to believe themselves neutral or remote, and therefore untouchable by war.
The characters in the novel have complex relationships with technology: they all know that their lives will shortly end because technological advances have made it possible to eliminate all life with one war, but at the same time, they themselves are unable to abandon their attachment to machines. The qualifying heats for the Australian Grand Prix, for instance, illustrates the dangerous relationship between humans and machines. Although technological gadgets are bringing the world to the end, humans are still in love with these gadgets. At the racetrack, people are more concerned about proving the efficiency of their machines than the safety of the drivers or spectators. Like those who created and used the atomic bomb, the racecar drivers are ready and willing to use technology, but are unwilling to take responsibility for its potential dangers.
Many of the individual characters in the novel show a love for machines. John, for instance, loves his Ferrari. Mary demands an electric lawn mower even though she will die in a few days. Even when Lieutenant Sunderstrom is surrounded by death and destruction in his coastal expedition near Seattle, he still takes time to admire the transmitter sending the radio signal, and he even goes as far as to look for the name of the machine's manufacturer. Sunderstrom cannot bear the prospect of the machine wearing out and breaking, so he turns it off, giving it a more humane death than that experienced by most of the war victims. Efficient, anonymous machines have led to the destruction of humanity, but Sunderstrom, like many other characters in the novel, is still in awe of these scientific creations. Yeoman Swain is another who cannot resist the charm of well-oiled machines. Even though he has just found all his loved ones dead, he is still happy because he has a car and a motorboat. People care so much about technology that now many of them choose machines are their final companions: both Moira and John take their pills in cars. Although this relationship with technology is ironic, Shute does not mock the human love for machines; he merely explores the fact that this love exists.
Moira highlights the dangers of knowledge when she flippantly asks if the Australian government will leave a record of how to make a cobalt bomb. Her remark is all the more powerful because she says it jokingly. While science is sometimes good for human society, technology has also led to its ruin. Radiation is the only lasting legacy of human scientific knowledge, making the link between knowledge and destruction clear.
While scientists should be horrified about the war they helped create, they continue to objectively conduct experiments and search for knowledge. John declares he will enjoy discovering the effects of radiation poisoning, not considering the moral and ethical implications of doing frivolous while so many lives are being lost. It is this scientific objectivity and detachment that made it possible for researchers to create the bombs in the first place. Moira respond sarcastically to John's shocking comments, but John is never fully criticized for his viewpoint. Shute writes like the objective scientist that he was in real life: he observes human behavior, but does not criticize it, leaving readers to draw their own moral and ethical conclusions.