Language

Imagine a hierarchy:

(1) Mechanincal, natural.

At this level, we describe everything in terms of physical interactions. It is a world without semantic content.

There will appear to be only one way of describing the world mechanically, and we might think of this as 'reality'.

(2) Signalling

At this level, we divide the world into systems and sub-systems. These have formal characteristics which might be instantiated in a number of different physical ways. Each unit is attached to one or more other units by a 'channel' which has a 'band width'. The bandwidth is the number of different signals the channel can carry. Channels are asynchronous - they carry signals in one direction only. For synchronous signalling, we need more than one channel (even if both might be implemeted using the same physical substrate).

To be a channel, at least one possible signal must be 'useful'. By this, I mean something like: we can specifiy the conditions under which it would be sent, and what effect it has on its recipient.

The formal characteristics of the system as the rules that describe the behaviour of the units and the structure of the signals.

There will always be more than one way of dividing up level 1 in this way - it will be a matter of taste or convenience whether we describe some things in terms as internal structure of individual units or in terms of sets of interacting sub-units.

(3) Semantic

At this level, we give the signals and the behaviours 'meanings'. These are always provisional (Kripke). Perhaps we might say that the a meaning interpretation is a 'model' of the system, but perhaps this would be confusing.

In any case, this is the level at this we introduce intentional content. We can say 'Unit A has told Unit B that the temperature has reached 0 degrees', or 'Unit A has instructed Unit B to switch on the heater'.

(4) Validity attributing

A signal can be interpreted as an adjudication on the correctness or incorrectness of (a) a semantic interpretation or (b) its intentional content. Things get pretty wobbly at this stage. What is really going on here?

Particularly difficult issues arise if we interpret a signal as adjudicating on the correctness of our interpretation of it.

Is this a model people use? It looks like it to me. It can be partly 'unpacked' in some cases, and this contributes to the illusion.

But the whole thing is an 'interpretation' ...