This development raises the central question of Simon Gleeson’s book: can virtual currency systems be fitted into the existing structures of monetary law? The author’s answer is that they can, provided we take a sufficiently flexible view of legal doctrines that evolved when the monetary system was grounded on coins struck from precious metals. The legal details based on those now-superseded forms of money should not hinder development.

The chapters in the book divide into two main topics. The first six chapters bear out the title of the book. They make a broad conceptual argument about the nature of money, understood as a social, economic and legal institution. Here, for example, the author takes on the relationship between the creation of money and the exercise of state sovereignty; the use of credit relationships in payments; and the reasons why money has a value recognised by social usage or by the law.

These six chapters of the book warrant a careful reading, even by readers who are impatient for answers on specific points of legal doctrine. They are full of salutary reminders, especially to readers who may overestimate the differences between virtual currencies and traditional forms of money. I shall mention a few of them. As the author shows, neither form of money has any tangible existence. Both are simply tokens representing notional value. They exist solely for the purpose of being transferred, usually for some other value received (Chapter 1.2). The value of money comes from the collective confidence of the people holding it that they can transfer it in complete discharge of a monetary obligation. Present confidence as to future use explains the exchange value of money, whether it consists in virtual currency units recorded on a blockchain or credit units recorded in a customer’s bank account. While the structures that support that exchange value may differ