While reading the book I could not help, but to notice the 2 major themes of the story. Since I only have a page I will revert to only one. The first is of course "the prodigal son" theme. I feel that the plot of the story is largely held together by an undertone of the religious theme that hints throughout the tale. In the first chapter of the novel you realize that the warning that Crusoe receives from his father, is prophetic and foretells what is to happen. Crusoe going against his father's advice, which is to stay home or terrible fate awaits him, of course leaves home and the result is fateful. .
At different times during his travels Crusoe falls into hardship and each time he begs for God's help and every time the situation improves he returns back to his old ways. At one point he takes part in a slave trade and God punishes him by sending him to a deserted island. Crusoe tries to make it on his own without asking for God's help, but when he comes down with an illness, he resorts to his help and becomes a "born again" Christian. From angry selfish man that he was when he left England, he becomes a virtuous and kind human being. God rewards his faith by sending him a companion in a form of essentially a slave (ironic). Crusoe treats Friday with great kindness and eventually converts him into Christianity. .
Upon his return to England, he does not take the credit for escaping of the island himself, but rather attributes it to God. For which God again rewards him with a wife and 2 kids.