Would you say that a laser-pointer's beam is a property of a body?
No.
Next question, please. Oh yes, Jim asked one.
If one takes a laser pointer's beam (say a nanosecond flash, about
30 cm long) as a physical system I have no trouble seeing it as
being well defined and, in my rational realist philosophy, it has
the property of reality, objective reality if you will. The system
exists independently of whether or not it is being observed, and
all observers can agree upon its extent and boundaries.
The energy of this system has no objective reality whatever. It is
an abstraction, a quantity which has meaning and utility only when
one defines a frame of reference in which to reckon it. Different
observers may ascribe to the system different energies. Observers
in noninertial frames may even find that the system's energy
varies with time!
I will point out that the size and duration of the system are,
likewise, abstractions.
Try to stop thinking of energy as being concrete. It is abstract
and will always be so. It is a quantity which we learn to reckon,
and which, magically, seems to be the same regardless of any other
changes which occur in an isolated physical system. That property
makes us think of other things which do have objective reality
(e.g. water*) and which are similarly conserved, and which flows.
There is always a chance for error when one reifies a metaphor.
Leigh
*I'm always tempted to say "money", but of course that is absurd.