If bitcoin can be converted into fiat currencies at a lower transaction cost than the fiat-to-fiat conversions made by banks and credit card companies, it’s a superior means of exchange.

One of the most common comments I hear from bitcoin skeptics goes something like this: Bitcoin isn’t real money until I can buy a cup of coffee with it.

In other words, bitcoin fails the first of the two core tests of “money”: that it is a means of exchange and a store of value. If we can’t buy a cup of coffee with bitcoin, it obviously doesn’t qualify as a means of exchange.

The confusion here is the same one that plagues the conventional understanding of the foreign exchange markets: people confuse exchange and convertibility, which are both flows, i.e. transactions.

Here’s an illustration of the difference.

Let’s say Hipster Coffee Bar accepts payment in bitcoin (BTC) for a cup of coffee. In the U.S., the coffee bar accepts the BTC as payment, which is then converted into the local currency, the U.S. dollar, to pay rent, employees’ wages and so on.

The Hipster Coffee Bar branch in Mexico converts the BTC into pesos, the branch in Thailand converts the BTC into baht, and so on around the world.

Another coffee shop, Most Excellent Coffee, doesn’t accept bitcoin in exchange for a cup of coffee. So when I enter Most Excellent Coffee, I convert a sum of BTC into U.S. dollars if I’m in the US, to pesos if I’m in Mexico or into baht if I’m in Thailand, and proceed to buy the cup of coffee.

You see the point: what matters isn’t whether the coffee shop accepts bitcoin directly; what matters is whether bitcoin is easily convertible to the local fiat currency. Put another way: convertibility rests on the recognition that the “money” is a reliable store of value that can be converted into a variety of other currencies.

As long as the cost of converting one form of “money” into another form of “money” is fast and low-cost (i.e. nearly frictionless), then it no longer matters whether the “money” in question can be used directly in an exchange or not.