> I'd say that can continue indefinitely, so long as the debt-to-GDP ratio remains manageable.

What's the quote about "To believe you can have infinite exponential growth in a finite world means you are either crazy, or an economist."

Actually my statement doesn't depend on exponential growth. If in future GDP were to switch from exponential to logarithmic growth, debt would still be serviceable as long as it also switched to logarithmic growth.

Come on, that's silly. At some point, for all intents and purposes in the real world, logarithmic growth would essentially mean "no growth". Splitting hairs between the continuous math and the math to a reasonable level of precision doesn't add clarity to your statement.

OK maybe over hundreds of years US GDP will go from exponential growth to linear growth, to logarithmic growth, to eventually "no growth". If total debt mirrors this trajectory, can't the US government continue repaying its debts over this period, even at the "no growth" stage?

Infinite != indefinite :)

USG have a long history of servicing it's debts by taking on more debt. Not that there is anything unusual with that pattern.

The US never pays back, they re finance the debts. Ad infinitum. I mean does anyone think that at this point the US could STOP the deficit? Let alone turn it into a surplus and start buying back debt?

US is too big to fail and rich people have to put their money somewhere. At least with US Treasury bonds you get a small but reliable return. So the train keeps going.

It happened under Clinton, admittedly with the advantage of a roaring economy. I won't rule out completely out, though from today's viewpoint it certainly doesn't look promising.

Well my country DOES try to balance the budget because otherwise the interest rates on the bonds we put out has to increase. But the US is special, it is virtually exempt from the normal laws of economics due to its superpower status.