Marx's point is that philosophy has not been used to practical ends. Though philosophers produce abstract ideas about the world, people do not adapt these abstractions into making practical changes in the world. In other words, philosophy is entirely abstract—with little connection to one's everyday life.
If this statement were applied to literature, it would mean that writers take on the abstract elements of life rather than address the practicalities of life. The question is whether writers, rather than basing their works on abstractions or larger themes, should instead turn to addressing ways people can change reality. Good literature, it could be argued, accomplishes both these ends. It deals with the larger conditions of human existence through examining the ways people live and poses ideas about how people can change.
Marx's brief essay "Theses on Feuerbach" ends with the words:
The philosophers have only interpreted the world, in various ways; the point is to change it.
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