  In this article we argue that in quantum mechanics, and in opposition to
classical physics, it is impossible to say that an isolated quantum system
"owns" a physical property. Some properties of the system, its mass for
example, belong to it in a sense close to that of classical physics; but most
often a property must be attributed to the system within a context. We give
simple motivations for adopting this point of view, and show that it clarifies
many issues in quantum physics.
