[from Mary Powers 9903.11]
Tracy:
You say that "when engineering a thermostatic system...the gadget called
'thermostat' is only the comparator portion of the device".
I don't think so. Thermostats include the sensor, the reference signal, and
the error signal as well as the comparator. The main thing missing is the
actuator, the device that is activated by the error signal and that does the
work in the outside world that affects the input. If that is included, then
so must all environmental disturbances. Indeed, disturbances and actuators
are part of the system as a whole, but for PCT purposes we have been mainly
concerned with a novel theory of the neural, "inside" part of the system,
always keeping in mind (though perhaps not making clear enough) that the
loop closes through the "outside", which includes muscles and glands as well
as events outside the skin.
Glenn Manry:
(please post your name and date at the head of your posts)
You object to Marc Abrams statement that PCT is not a metaphor. You ask:
"If theory is not a representation of something by using something else,
then please tell me what it is".
Theory is the principles explaining a body of fact.
Metaphor is a figure of speech in which a word or phrase literally denoting
one kind of object or idea is used in place of another to suggest a likeness
or analogy between them. (Thank you, Mr Webster)
Control theory is not a metaphorical representation. It is not an analogy.
It is a fact that living systems control. PCT explains that fact by using
the principles of control theory. It says that because living systems
control, they must have a certain kind of organization - one that is common
to all control systems (this of course is provisional, as are all theories:
there may be other ways to be organized that make control possible).
It is a metaphor to say "my heart is broken".
It is not a metaphor to say "my heart is a pump".
It is a metaphor to say "I've had a brainstorm".
It is not a metaphor to say "My brain is organized to control perceptions" -
but you don't have to know that in order to do it, any more than you have to
know how your heart works in order for it to beat.
Mary P.