Marx argues that communism is not just desirable, but inevitable. We may not know precisely when it will arrive, but we can be absolutely certain that it will do eventually, and that when it does it will be as the result of capitalism’s many internal contradictions.

Marx’s theory was based on the notion of progressive immiseration. That is to say, he believed that, as capitalism developed, it would inevitably impoverish more and more of the proletariat or working classes, thus generating greater inequalities between them and the bourgeoisie, the owners of the means of production. On this reading, the development of technology accelerates the headlong drive for profit, causing capitalists to drive down wages. In turn, this will drive the proletariat even deeper into wretched poverty.

At the same time, the proletariat, under the guidance of professional revolutionaries like Marx and Engels, would develop an awareness of their class interests. In other words, they would develop what Marx calls "class consciousness."

Once this stage has been achieved, it is just a matter of time before the proletariat get off their knees, throw off their chains, and rise to up to stage a cataclysmic revolution against the capitalist system. According to Marx, this is an inevitability and will eventually usher in the complete abolition of the capitalist system and its replacement with communism.