>>2819212>Historical determinism to predict future I'm frankly too lazy to write an actual effort post, but the fundamental problem is that Popper has a tendency to:
<1. consider "pseudoscience" (i.e., unprovable claims) to be false<2. treat Hegelian historicism as unfalsifiable and definite facts about the futureNeither of which are true. Marx isn't making a historicism. He's not saying that communism has to emerge with certainty in the post-capitalist world order. He's simply saying that the end of political development ends with communism.
Think of it this way: the state and its development change because of multiple conditions (a revolution, class conflict, instability, conquest, etc.). Now, when we look at the state, we can see that it mostly serves as a means to reproduce capitalist reified relations, to ensure property for a specific group of people.
As such, when the conditions that make the state change disappear, political development ceases. This isn't to say that event X can't happen under communism, or that regression is impossible, but that the conditions which create change in the first place (namely, class conflict) disappear. Marx radicalizes this idea by positing that the state, as it exists, only serves the purpose of protecting the class interests of the bourgeoisie, and that, as such, if communism does arise, the lack of class distinction will lead to the withering of the state.
Now, the reason why Marx claims that communism will likely arise is simply from a sociological standpoint: the globalization of the bourgeoisie and the creation of a capitalist hegemonic mode of production has converged toward the establishment of only two classes, the proletariat and the bourgeoisie.
For instance, a feudal society like France in the Middle Ages had many classes and centers of power: it had the Church, the landed gentry, the bourgeoisie, the robe gentry (state admins and the king), the peasants, etc. Only one of them took power, leaving the rest to be subject to the now bourgeois power.
But in our current times, there is no such composition. Sure, there might be some variations in the interests of a white-collar Boston man and his Indian delivery driver, but they still nonetheless share the same composite interest in overcoming the bourgeoisie. As such, Marx is not claiming that communism has to prevail, but that it is simply the probable trend, and that it will likely usher in a new age where political development as we know it ceases.
Popper takes issue with this because he's retarded and doesn't understand Hegel or Marx. Instead, he thinks that they are making scientific claims that are to be empirically demonstrated. In doing so, he shows his lack of understanding of what communism is and of the fundamental nature of Marx's claims.