Money has always been a particular problem for revolutionaries and anti-capitalists. What will money look like 'after the revolution'? How will it function? Will it exist at all? It's hard to answer the question if you don't know what money actually is. Proposing to eliminate it entirely seems utopian and naive.
It affects every aspect of our lives, is often said to be the root of all evil, and the analysis of the world that it makes possible - what we call 'the economy' - is so important to us that economists have become the high priests of our society. Yet, oddly, there is absolutely no consensus among economists about what money really is.