You seem to have a decent grasp on the regression theorem. I consider the RT to be one of the most impressive works of Austrian value theory in actual application to date. I’m sure that there are other similar applications out there that haven’t been thought of yet.
Anyway, one of the insightful things that RT really emphasizes is that there is no intrinsic value to money. A dollar is only worth a dollar because by and large and in general individuals perceive it to be so, and because of this there are factors that correct any misestimates of the value of money. At any rate, because a dollar could theoretically be worth a thousand ears of grain, or none at all, there needs to be some value that we can anchor the dollar to because money as a medium of exchange has no value per se. Everything else gains value out of direct or indirect utility satisfaction, therefore the only way that money can derive value is off of this. Therefore at some point or other money has to have this property of utility satisfaction in some way other than through exchange for other goods, namely some good that it “equates to”. Something that better exemplifies this is the fact that money doesn’t even have to be what we traditionally think of as “money”. Money, a vague term in a lot of ways, is nothing other than a generally accepted medium of exchange, something that people generally will exchange things for. It could be butter, bottle caps, or hair follicles depending upon situation and preferences. Unless a certain good has the properties of being generally desired then there’s no reason why it would emerge as money.
Think of it as starting potential. to become a money something must have extrinsic value (by which I don’t mean that the value isn’t subjective, merely that the money represents something which directly grants utility, rather than something which is exchanged against an array of goods in return for money), however because exchange is so valuable, the non-exchange values of money, the indirect values of money soon take a back seat. Theoretically the moment nearly all prices emerge in terms of gold the government could then declare an entirely fiat standard and everything would be relatively fine because, so long as confidence in the stability of the currency is assured, the primary source of value for the currency is its use in exchange, not its physical use.
As for your question about the ability of governments to assign value to currency through taxes, while this is next to impossible to do in our real world since the world economy is interconnected and you couldn’t start an advanced economy in the absence of currency, it nonetheless poses an interesting possibility. If we take a society that is currently engaging in barter with no clearly dominant money, then why couldn’t a government merely attach its currency to a good and demand that? If the government declared a dollar worth 10 cabbages, then it would need to issue just enough money relative to cabbages or else the price of cabbages would plummet, people would alter their exchange rates just to avoid accepting the money. Nor can the government assign taxes to income since there is no monetary income to be taxed. I can’t charge you for 10 percent of your income since it’s not obvious what that is. Therefore I really think that it’s impossible for the government to do since people would just alter their behavior to avoid paying the taxes.
A universal flat tax might work, but I think you’ll have similar alterations in behavior. For instance if the government says everyone owes it 100 dollars a year then you have two problems: the first is that the government would arbitrarily have to decide what to confiscate what it would take if this didn’t happen, in which case it would have the same problem above as the values of those goods would drop. Secondly people would just hold money as a means of paying taxes unless the first condition altered their behavior.
The problem is that everything is subjective.
Anyway, back to your actual question. Debit cards are just a means of changing physical money into digital money that is more portable. The money already exists and is just changed into a different form, it’s no different than a checking account. Meanwhile credit cards perform services similar to a bank loan. The credit card company (I believe) has the money and so it pays it directly. It assumes that the debtor will someday have the money, and therefore the assumption of future money is what is being exchanged. Physical good for current money for future money.
Does this answer your question? If you have any other questions about AE feel free to ask me. I’ll answer your questions, although I can’t promise that I’ll do so in a straightforward or simple way… I will try though!