Daniel Defoe's novel Robinson Crusoe tells the story of a man cast away on an isolated island who attempts to create a life for himself. An important thing to note in reading the novel is that Daniel Defoe was himself a Dissenter and a strong advocate for the rights of Dissenters to freedom of conscience. Many of his protagonist's spiritual developments reflect this.
The first theme in the book is one of survival. In his experience being shipwrecked, Crusoe must think about what is absolutely necessary for physical survival.
The theme of survival leads to a second theme, which is awareness that in our lives in civilization we constantly long for many things we do not actually need. Thus Crusoe reflects on the theme, or sin, of covetousness:
Those people cannot enjoy comfortably what God has given them because they see and covet what He has not given them. All of our discontents for what we want appear to me to spring from want of thankfulness for what we have.
The next theme is spiritual growth. Away from the regular life of civilization Crusoe begins to understand that religion does not require elaborate rituals or priests, but faith, a position which was the central tenet of many Dissenters.
Another important theme is the value of self-sufficiency and hard work. Crusoe makes a life for himself on the island by setting goals and achieving them through self-discipline and hard work, a point that might be expressed in Virgil's phrase "labor omnia vincit."
Another major theme is colonialism as it appears in Crusoe's relationship to Friday, which is a microcosm of the British empire's relationships with indigenous peoples.
An additional theme is fear. It is only by overcoming his fears that Crusoe can create a happy life on the island.
A final theme is money, which is essential in the civilized world, but useless in the world of the island.