Well, that's not the only reason economics isn't a science, and the reason I despise economics is that economists pretend they're scientists after all: they use math to obscure the far-outness of their premises.

You speak of "direct borrowing from humanity." Is this fortune for each person borrowed or gifted? If it's borrowed, there would have to be a way to pay it back; otherwise, someone is losing out in the exchange, and the system wouldn't be capitalistic. Who's putting up the collateral for the loan, and why would they do so? To be ethical? Studies show that rich people are generally less ethical than poor ones.

What would be the incentive of bankers to be ethical in this regard? Would the investment in all of humanity be wise or wasteful? Wouldn't many people squander the money, leaving them right back where they started? This is what happens to some lottery winners. We don't know the value of free money. This is also supposed to be the problem with collectivist societies: we lose the incentive to work. But maybe we should be playing more than working?

I'm playing devil's advocate here, to some extent.