My understanding of MMT (unburdened by any formal econ training) is that government spending financed by debt in that government's own currency is OK if and only if the society has — or can quickly enough build — sufficient productive capacity to handle the increased demand that will be caused by the increase in the money supply. I found Dr. Stephanie Kelton's book The Deficit Myth to be a very-accessible explanation that made intuitive sense (which of course is always dangerous).
The perhaps-facile analogy is pump-priming, a.k.a. fiscal stimulus, summed up in the old Kingston Trio song Desert Pete: You come across a hand-operated water pump in a well in the desert (hah!), with a bottle full of water sitting there, and a note explaining: You can "borrow" the water and use it to prime the pump; once you get the pump going: "Drink all the water you can hold, wash your face, cool your feet | Leave the bottle full for others | Thank you kindly, Desert Pete."
But that only works if the pump is working and has sufficient "raw material" (water in the well). And if you drink most of the bottle of water (borrowing for consumption instead of for boosting productive capacity), then the pump won't draw water, and you'll angrily claim that priming it doesn't work. As Desert Pete warned, "Now there's just enough to prime it with, so don't you go drinkin' first. Just pour it in and pump like mad and, buddy, you'll quench your thirst."
The lack of acceptance of MMT among mainstream economists is of course a red flag. But then in medicine, Marshall and Warren asserted — correctly — that many common stomach ulcers were caused by Helicobacter pylori bacteria and could readily be cured with cheap antibiotics instead of with major surgery. They were scorned by mainstream physicians and surgeons protecting vested interests. And eventually they were awarded the Nobel Prize in Medicine.
So lack of acceptance isn't dispositive; as I read somewhere but can't find online, old economics ideas don't die out until old economists do. (Or maybe it was physicists?)
The perhaps-facile analogy is pump-priming, a.k.a. fiscal stimulus, summed up in the old Kingston Trio song Desert Pete: You come across a hand-operated water pump in a well in the desert (hah!), with a bottle full of water sitting there, and a note explaining: You can "borrow" the water and use it to prime the pump; once you get the pump going: "Drink all the water you can hold, wash your face, cool your feet | Leave the bottle full for others | Thank you kindly, Desert Pete."
But that only works if the pump is working and has sufficient "raw material" (water in the well). And if you drink most of the bottle of water (borrowing for consumption instead of for boosting productive capacity), then the pump won't draw water, and you'll angrily claim that priming it doesn't work. As Desert Pete warned, "Now there's just enough to prime it with, so don't you go drinkin' first. Just pour it in and pump like mad and, buddy, you'll quench your thirst."
The lack of acceptance of MMT among mainstream economists is of course a red flag. But then in medicine, Marshall and Warren asserted — correctly — that many common stomach ulcers were caused by Helicobacter pylori bacteria and could readily be cured with cheap antibiotics instead of with major surgery. They were scorned by mainstream physicians and surgeons protecting vested interests. And eventually they were awarded the Nobel Prize in Medicine.
So lack of acceptance isn't dispositive; as I read somewhere but can't find online, old economics ideas don't die out until old economists do. (Or maybe it was physicists?)
[0] https://www.amazon.com/Deficit-Myth-Monetary-Peoples-Economy...
[1] https://genius.com/The-kingston-trio-desert-pete-lyrics