Com’on Alex, you are giving collective accusations. When you have seen Martin doing that? Or someone else (but one) in CSGnet list?
Eetu
···
Sure, Martin, but if one bypasses mathematical correctness, ignores the rules of evidence, and
fails at logical reasoning, no matter how one BELIEVES (!!) “PCT to be essentially not only correct, but necessary” ,
what is said and done is not science anymore —not even philosophy— but some so sort of pseudo-scientific religious email jousting which, honestly, is what CSGnet looks like most of the time.
On Tue, Nov 7, 2017 at 5:41 AM, Martin Taylor mmt-csg@mmtaylor.net wrote:
[Martin Taylor 2017.11.06.08.40]
On 2017/11/6 2:51 AM, Alex Gomez-Marin wrote:
… the whole problem with most of PCT attitude now is that since you know from god that you are right, …
It is several years since I last commented on my reasons for believing PCT to be essentially not only correct, but necessary, given the scientific environment in which researchers have lived for the last 400 years or so – a belief that if one branch of science
seems to contradict another, something is wrong.
Classical physics of the Newtonian kind may not account for everything we observe, but so long as we avoid quantum and relativity-level issues (two areas of science that do seem to produce contradictions with each other, but not with low speed human-scale energy
Newtonian laws), we can take the laws of thermodynamics as a basic truth. One direct consequence of those laws is that in the absence of a through energy flow, no structure can survive indefinitely in an environment that is less organized than itself – "* In
a closed system, entropy increases toward a maximum* ". In other words, an intake of energy and a later export of the same amount of energy in less structured form is an absolute requirement for the maintenance of structure, whether the structure is alive
or not.
We know that by way of feedback, energy flows can result in “self-organized” structures such as vortices, and that all living things are self-organized structures. But we must go beyond simply saying “self-organized structure”, and consider how our structures
survive the assaults from the environment that are the reasons why structures decay and deteriorate without through energy flows. Boltzmann and Gibbs provided answers that were precise in quite disorganized systems such as gases, but their argument has much
wider applicability. In simple terms, the argument is that if some complex thing breaks, random effects are highly unlikely to put it back together as it was.
There are two ways, passive and active, to deal with situations in which something might break because of influences from outside. Passive ways include shields and shells that separate the structure from the environment, splitting the Universe into “the structure”
and “the rest of the Universe”, or into “inside” and “outside”. There are two kinds of active process, one being to act on the environment to prevent damage before it happens, while the other is to repair the damage. The latter is the domain of feedback processes
we generally call “homeostasis”, while control does both, though mainly prevention. The self-organizing energy flow (food in, heat and waste out) is manifest in the processes of both control and homeostasis.
“Homeostasis” versus “control”: I use these terms slightly differently, though it might be legitimate to consider them as examples of the same process distinguished only by where the perception and environmental correlate exist, saying that perceptual control
happens when the correlate is in the external environment, homeostasis when they are both inside the shell or skin. I don’t make that distinction. Instead, I treat homeostasis is the result of generic negative feedback loops that as completely within the skin
bag, no matter how long the loops may be or how complex their feedback structure.
Perceptual control, on the other hand, I take to occur when the state of one internal variable is brought to some specified value and maintained near that value but directed actions on some other variable, which is typically but not necessarily in the external
environment. Perceptual control has a necessary asymmetry in the loop, in that the energy transfer from the “other variable” to the controlled perception is much less than in the other direction, thus ensuring that entropy is exported rather than imported.
Homeostasis does not require such an asymmetry.
This Figure suggests one possible way of looking at the division of responsibilities among homeostasis, the shell or skin, and perceptual control. “Incoming” lines represent discrete external influences from the external environment. Those terminating in circles
are absorbed either by by perceptual control or (in one instance) by the shell. Relatively few get through the shell or skin to the homeostatic interior where the structure is repaired and maintained in good condition. The figure ignores the possibility of
control loops for which both the perception and the property subject to control action are both inside the shell or skin.
Shells cannot isolate the structure entirely from the rest of the Universe, and homeostatic processes alone might be hard-pressed to repair all damage caused by influences from the outer world. To support them and enable the continued existence of any complex
structure is the role of perceptual control, which can be imagined as a diffuse active shell (grey in the figure) around the organism that reduces the load on the passive shell or skin by decreasing the entropy of the surrounding local environment.
Perceptual control extends the region of low entropy from the structured interior to the local region of the exterior, reducing the structure-destroying entropy flow to the interior. Rather than exposing the shell or skin to the full damaging influence of the
environment, the environment becomes structured in ways that reduce the likelihood of effects on the interior that would require repairs by internal feedback processes.
In order to structure (reduce the entropy of) the local environment, the organism must be able to act on aspects of that environment. In order to act on it in a way that increases the local structure (decreases the local entropy), the action cannot be random
with respect to the way the environment happens to be, because random effects by their very nature increase the local entropy. It must move the environment from its current configuration into a particular configuration, and that is unlikely to be accomplished
by random actions on the environment.
Just perceiving and acting upon properties (aspects) of the environment does not necessarily reduce the local entropy, or increase the local structure. To do that, the property being perceived and influenced by the organism must be changed in very particular
ways, not randomly. The property must be brought to a state that will bring the perception to some specific state or one of a small set of states. In other words, perceptual control is required for the survival of any organism that does more than sit inactive
inside a shell, repairing internal damage by homeostatic processes and passively somehow taking in and exporting the energy needed to keep those processes going.
Putting this together, except in the extreme case of the inactive organism in a shell, thermodynamic considerations require that some form of PCT be correct, in the sense of being a “Law of life” in the way that “Every action has an equal and opposite reaction”
is a Law of Nature.
Perceptual Control Theory.
Perceptual control may be required by thermodynamic considerations, but PCT (Perceptual Control
Theory ) has many possible forms, of which the purely hierarchic (no within-level lateral perceptual or output links) form described by Powers is just one. Which one evolution has given us may not be the same for all organisms. Indeed, in detail
it cannot be the same for, say, organisms that sense electric fields as it is for organisms that don’t. But the principle that all living organisms that act on the environment must do so in ways that on average reduce the local entropy, reducing the probability
that their shell or skin will be breached and their structure damaged, holds, whatever the details for a particular species or individual.In the past, for personal convenience I have divided the possible forms of PCT into three completely arbitrary classes: (1) HPCT, the pure form of Powers’s hierarchy as it evolved over time in his writing, which reduces local entropy by treating individual
degrees of freedom independently; (2) Extended or augmented HPCT, which is based on HPCT but includes elements that are not in the Powers structure, such as vector rather than scalar perceptions, lateral interconnections within levels, or treats the effects
of signal paths being individual nerve fibres rather than bundles that convey discrete “neural currents”; (3) Anything else so long as perceptual control reduces the local entropy of the environment in ways that support the shell, such as, for example, a one-level
structure of independent perceptual controls that correspond to independent properties of the environment. Any form of PCT is permitted by thermodynamic considerations, but some are more efficient than others and therefore have a better chance of surviving
evolutionary (and reorganizational) processes.In sum, I do not believe it is possible to have a science of living things that is not ultimately based in some form of PCT. That belief has nothing to do with access to any god who might or might not have been involved in constructing a Universe that works
this way.Martin