[amluto]

> Also, I'm not able to really follow what he means by "money = assets in the future".

I’m guessing it’s one of two things:

1. A transaction might fail. If you enter a transaction into your bank’s website or your credit card company’s website, you should probably record it in your ledger right away. But the transaction might get canceled for any number of reasons. And the money will not actually move instantly, at least in the US with some of the slower money moving mechanisms.

2. In stocks and other markets, settlement is not immediate. A trade is actually a promise by the parties to deliver the assets being traded at a specific time or range of times in the future. One probably could model this with “in transit” accounts, but that sounds quite unpleasant.

FWIW, I’ve never really been happy with any way that I’ve seen accounting systems model accruals and things in transit. I’ve seen actual professional accountants thoroughly lose track of balance sheet assets that are worth an exactly known amount of cash but are a little bit intangible in the sense that they’re not in a bank account with a nice monthly statement.

[BlueTemplar]

Money never moves instantly : light speed is a limit (and also something can always happen to the message(s).

[Spivak]

This isn't really the issue I think, the question is whether money always moves fast enough that you can model them differently— as an atomic object that either exists and is complete or doesn't exits at all. Can you just have the caller wait some milliseconds and either get an error or a success meaning it's done? The answer is of course no but there are plenty of things that can be modeled this way.