If we were fancy-pants literary critics, we might say that The Cay is a meditation on sacrificial love. What do we mean by that? Well, the novel really wants us to think about what it means to give things up – either for the people we love or for the good of humanity.
There are tons of super-heroic acts of sacrifice throughout this novel. First, there's the backdrop of World War II and the people who lose their lives during the conflict. Phillip's dad doesn't die in the war, but he does stay on the island out of duty to his country while the rest of his family leaves. Then there are the sacrifices Timothy makes to protect Phillip on the cay. In the ultimate act of selflessness, Timothy shelters Phillip from the hurricane with his own body, sacrificing his life. The novel holds up these instances of sacrifice as heroic and necessary deeds in the face of senseless violence.
In The Cay, sacrifice is the greatest form of love.