Complex sentence: Indeed, many features of the Marxist view of the world's political economy had been worked out in great detail, but Marx needed to write down all of the details of his economic world view to further clarify the new economic theory in his own mind.
Split into simpler sentences: Indeed, many features of the Marxist view of the world's political economy had been worked out in great detail. However, Marx needed to write down all of the details of his economic world view to further clarify the new economic theory in his own mind.