Tante I think you picked up some of my concepts and not the others. It's the "payment system" that has to be currency agnostic, not the currency itself.

All a payments system is (at least any kind of industrial one) is a facility for shifting numbers around. You can't replace that with a blockchain any more than you can replace a shopping list with the groceries themselves. The payments system is a way to get the trades TO the blockchain (or whatever clearing system is concerned).

No commercial entity in their right mind is going to deploy a payments system that is tied to a single currency denomination - that's one reason why you can't use realtime clearing systems at the point of sale. Another reason is that the trade has to be cached at various levels to support local business rules and priorities. For example, at the top of the tree comes a POS terminal (or eCommerce server) which is able to process the current order and take payment, but that doesn't mean a financial clearing transaction has to occur right there and then.

All that happens is that an order is received and a credit card number taken. There's the whole delivery processing that needs to take place and possibly various problem resolution phases which can range from revising the order to suit product availability to resolving wrongly entered products on a supermarket conveyor belt. As far as the customer was concerned, the sale was "instant" but that doesn't mean the payment at the clearing layer was instant. Blockchain properties have nothing to say about this because blockchains will not be involved except possibly way downstream.

I suppose it helps to have worked in and designed retail payment systems to fully appreciate all the complexity involved, but to illustrate the point just look at the cryptocurrency exchanges: blockchains fell at the very first hurdle. An exchange is a payments system but non of them use blockchains to facilitate the trade. If they did they'd grind to a halt because they couldn't cope with the diversity of performance, protocols or reliability. The trading function has to be abstracted away from the blockchain.

The same applies to the commercial world.

*********** However - Addendum: Whole "Nother" Dimension **************

Of course, all of the above applies to trading with "accounts" which forms the bulk of modern day commercial activity. Even if you don't have an account with the retailer you'll usually pay with a credit or debit card which references an account.

Meanwhile cryptocurrencies are a form of electronic "cash" so new criteria may apply. It remains to be seen how this will fit in. In other words blockchain payments would correspond to paying cash (i.e. paper notes) for goods. This is uncharted waters and the extent to which this financial domain can be exploited depends on other factors such as demand from the public to make blockchain payments for stuff. I admit to not having thought enough about this myself but I think it's an area that needs to be far better understood than it is which is why I've been trying to raise consciousness about the various distinctions between capital assets, price denomination policies and payments systems lately.

I hope you enjoy thinking about it too and don't get a headache. If so, here you go...



P.S. I just thought of something else. Cash is a relative thing - it's basically DEFINED by the price denomination of the thing you're paying for. So if a good is priced at 500 USD and the seller says they want "cash" then that means they want $500 in paper notes. If you paid them in crypto for that trade they'd have to convert the crypto to arrive at their desired quantity and form of compensation, so in that case the crypto only qualifies as a "payments system", not really cash (from the product vendor's perspective). So what is and what isn't "cash" is a subjective term and the arbitrator is the price denomination of the trade.

See ? Lots of things to think about and wee strands of conceptual and terminology detail to untangle and properly define. Not completely intuitive.

P.P.S. Look what just arrived while I was typing...it's as if the blockchain was tipping me for rambling. Much oblidged