I think that this quote brings out Marx's idea of praxis that became such a strong part of his thinking and the resultant forces that owe their source to him. Marx's thought was different than other philosophical tenets of the time period because it was rooted in understanding and action as a result of this comprehension. Philosophy prior to Marx did not include the dimension of action. For example, what action can be taken out of Descartes? One will always think and always doubt. The resultant action of Cartesian thought is in the subjective and in the internal concsciousness. For Marx, though, philosophy is only good in terms of the action that is spurned from it. The trend of philosophy that remained chained to the realm of the subjective was something that was rebuked with Marxist thought. It is here where philosophy was moved into the realm of social justice and action. Praxis became the point where thought and action merged into one. The "interpretation" of philosophers that is alluded to in the quote is moved into action with Marx's thought and his analysis. In this light, literature and the printed word has to result in some level of social change or solidarity in order to present a transformative vision of art.