This argument between Mond and John the Savage centres around what freedom is. Mond believes that freedom is being free from disease, destruction and negative emotions, whereas the Savage sees it as being allowed to live without conditioning, according to nature and with all the negatives that come with this.
These differing ideas of freedom and human nature can be seen in the philosophy of two different thinkers: Plato and Nietzsche. Plato believed that people could only be free if they controlled their chaotic and destructive natures and learnt of the Good. This would allow the state to be stable and happy. Nietzsche argued that humans are naturally chaotic, and that this is what it means to be free. People can only be free if they live with their negative emotions as well as the positive ones, in a world of ups and downs.