Steven and Paul,
Having read some of Paul's comments in other blogs and threads, I do not think that Steven's last post is quite on the mark, about what Paul is saying.
Paul is, in effect, (incorrectly) saying that physics *should only* concern itself with the "source" of a "message", and not with either the message itself, or the mechanisms by which the message is detected/observed. In Newton's time, that was how physics was thought of. But people like Einstein and Heisenberg realized that there is no clear dividing line, between the observations of the source of a message, the message from the source, and the observer of the message.
Existentially they are different, which is Paul's point. But observational, they are not so distinct. Paul seems to think they should be. In classical physics, they were.
Consider Paul's statements:
"So the real question becomes, ... , how does what is generically true, actually manifest itself in the physical existence being investigated."
"We know there is something which exists independently of the mechanisms which enable its detection."
Now consider Paul's earlier example:
"To my left there is a waste basket, and a chair with a dog on it. A photon based representation of whatever constitutes the physically existent state which we are referring to as waste basket is currently being received by the chair, and vice versa. In just the same way as the dog and I are receiving such physical input. The physics is the same. The dog and I can subsequently process what is received, indeed, we do it differently. But that is irrelevant to the physics. The processes certainly need to be known, so that we can understand how the output from that processing relates to the input.
But that input was an independent physically existent entity. However, it was not the existential reality (ie what is usually referred to as reality), it was created as a result of an interaction with that."
Paul's "A photon based representation" = Rob's "message".
Paul's "input" = Rob's "source"
Paul seems to think that only the "source", the wastebaskets etc, are the proper subject matter for physics. The message is not, nor is the detection process. But photons themselves also exist, as a physical reality, and thus can be another proper subject of physics. But unlike the wastebasket, which does not directly interact with the detector, photons do interact with detectors. Hence, describing how photons behave, is proper physics. In other words, Paul does not seem to be considering that "A photon based representation", is not *just* a "representation", it is also "something which exists independently of the mechanisms which enable its detection", but also, independently of its source.
Sets of photons are just as real (whatever they may be) as sets of wastebaskets, chairs, dogs and people, independently of their possible interpretations as representations.
Rob McEachern