Someone was saying that even if using machines becomes cheaper than using humans, capitalist will still use humans because
"automation constitutes constant capital and human labour is variable capital
The Tendency for the Rate of Profit to Fall disproves that fact"
What do those mean?
I completely agree with how you approached it, the quotes you provided gave me pause when I first read them. Although in context I’m quite sure Marx really wasn’t thinking about AI, I have no explanation for his choice of words. If I had to speculate, I’d suggest that he didn’t think some tasks (e.g sorting by colour) could be done without some measure of intelligence, but that’s just one idea.