Why is this definitely true? Other economic/societal systems have fallen in the past. Why does that mean this one has to? Or is there some other reason why this statement is true?
I'm not trying to cast doubt upon this idea. I'm just trying to find out its justification, from a scientific perspective.
Cheers.
Lots of reasons, but here’s a big one no one’s said yet.
In book 3 of Capital, Marx talks about the Rate of Profit, measured as Profit/Investment. Even before Marx, this RoP had been measured to decrease over time. There are many theories as to why it does this, but Marx said it was because of the continual investment into new Capital. Regardless of the reason, the RoP has continued to fall over the centuries, to the point where now we are seeing the lowest RoP in capitalist history. This is very bad for capitalism, because the only driving force for capitalists to do anything is to make profit. But if the RoP ever reaches 0, there will be no more profit, and the system will no longer have the “fuel” to sustain itself.