In Jack London's works, struggle is a central theme influenced by his own experiences and the ideas of Friedrich Nietzsche, Charles Darwin, and Karl Marx.
In the context of Jack London's works, the narrator would most likely agree with the statement that struggle is a central theme.
London was influenced by the writings of Friedrich Nietzsche, Charles Darwin, and Karl Marx, all of whom saw struggle as a fundamental aspect of life.
London's own experiences, such as working in mills, sailing boats, and venturing to the Canadian Yukon in search of gold, shaped his perspective on struggle and informed his popular literature.