Fungibility and equality

The concept of “book” is vague. If a book is something with an ISBN, does that mean two copies of a book are equal if they have the same ISBN?

The answer probably depends on the lifecycle of a copy of a book. In a warehouse, all copies of a book are fungible, i.e. they can be exchanged with each other and nobody will care. Once sold, the copies become non-fungible.

Note last edited January 2022.
Backlinks: Equality in programming languages, Instances and equality.