Ok, If it was over your head, you were talking about a zero sum system.
With in the context of "relative wealth". Don't lose sight of the issue being debated here.
It's entirely obvious, even without a definition, A + B + C = 0.
You said that industrialism broke this equation to no longer be a zero sum system (A + B + C = X ; A + B + C + X = 0)
This is false because for this to be true, no net economic growth (and therefore, no wealth creation) could have ever occurred in the course of human history prior to the industrial revolution.
Nope. I even explained how net economic growth occurs. My point wasn't that economic growth never occurred, but that it occurred slowly enough and via methods that generally didn't directly impact the relative wealth question we're discussing that it could be largely ignored.
A nobleman who owned title to a large estate and surrounding lands gained control of the bounty of those lands. It could be correctly stated that the whole net sum produced on those lands was relatively fixed. It could thus be argued that if the nobleman takes a larger share of that bounty (makes himself more wealthy), then the consequence was increased poverty for those ho lived on and worked on his lands. This is the state of economics that existed more or less unchanged since man first started building cities and land titles and whatnot (a few thousand years). This was certainly the economic system with which Marx was familiar.
The industrial revolution changed that in one very obvious way: The rich guy who opens up a widget factory can gain a massively greater share of the wealth generated by the factory without actually making the people working in the factory any more poor. He pays them a set wage of $X/hour. Prior to industrialization, each worker produced some number of widgets over that time. Enter industrialization and each worker can be retrained to use the widget making machines and thus produce 10x as many widgets in the same amount of time. He's still paid the same wage, but the owner of the factory makes 10x as much, right?
That's the "problem" with Marx was talking about. He saw the owner gaining 10x more, but the worker making the same. His experience with economics was that such a great disparity, even if it appears on the surface to have no negative for the worker *must* actually have one in some way. The workers wage should become less worth relatively speaking, or some other effect would make his relatively low wage cause him harm. And if we were living in a past age where we just worked the laborers harder or longer hours to increase production, he'd have been right. But industrialization really did change economics in ways which the economists of the day had a hard time predicting.
The biggest change is that due to the increased volume of production now possibly from the same amount of labor, the predicted deflation of the value of wages those economists would expect was more than offset by the decrease in cost and increase in availability of products and services which average working people could not afford prior to that point. Suddenly, finely crafted (well, somewhat finely crafted) furniture was available to average people and not just the rich. Then things like running water, indoor plumbing and toilets, and automobiles, then washing machines, radios, telephones, TVs, computers, the internet, cell phones, and a host of other things became steadily available, not just to the richest people, but to even the modestly salaried workers.
He envisioned a future where capitalism would cause industrialization to focus wealth on the producers and poverty on the workers, with the workers lives getting progressively worse until eventually they would have to rise up as one and reshape the whole system. The reality, however, is that this didn't happen. The condition of the workers did not get worse. It got better. Even in the absence of unions acting on the assumption that if they didn't intervene things would get worse, things didn't get worse. They got better. It didn't happen all at once though. The positives took time.
What did happen is that enterprising people pointed at Marx's warnings, pointed at the dollar wealth gap (while ignoring the quality of life improvements going on all around them), and convinced people that if they didn't take some kind of drastic action, then the inevitable disaster for the working people would occur. They scared the people into supporting unions in some countries, adopting draconian laws in others, and in some into overthrowing their governments in some form of communist revolutions.
All of those things were unnecessary. The danger wasn't real. But it was (and still is) a means to gain power for those who can convince others to fear what might happen and give them power to help fight it. And I can forgive Marx for failing to see the truth. But it still boggles my mind that otherwise intelligent people still fall for the whole "If you don't join with us, those evil rich people will take everything!!!" arguments. The very process makes no sense. The economic system largely requires consumption of that increased production to work. It's in the wealthy's best interest to make sure that there are sufficient people with sufficient buying power in the economy to buy the things their factories make, right? Think about that. They want to employ as many people as possible, but they want them employed making useful things that other people will want to buy.
There's just no logical motive for the players in the free market to take everything away from everyone else and make them poor. I will point out for comparison though, that those who espouse socialist or communist systems absolutely do have a motive to make as many people poor as possible. It's their route to power and control. The free market tends to free those within it. And that's a threat to some people.