[FRIAM] Who's on Friston? Me and my Markov Blanket

[Steve Smith]

Great conversation, to which I can add little more than a few comments
as I feel I am scrambling to "catch up", at least with the "fusion" of
multiple things I already (thought I) understood but which are
converging in this topic/discussion:

EricS wrote:

> Steve, hi and thank you,
>
> Luckily, I actually was at that talk, so didn’t have to backfill.
>
> I don’t know what I think.  I have been aware of Karl’s work through
> various enthusiasts for it over the years, but there is such a
> firehose of volume that I wasn’t willing to start, for a “free energy
> principle”.  I agree that it is good he talks about inference and what
> I take to be causal reasoning in systems with feedbacks.
>
> I guess I would still like to hear the answer to the question Cris
> Moore asks: what are you adding, Karl, beyond what Judea Pearl was
> already doing by putting boundary states between interiors and
> exteriors in Boolean networks, to define criteria of conditional
> independence?  I don’t know that Karl ever gave an answer to that in
> which I saw a crisp statement of content.
>
> To the extent that I thought I roughly followed the talk, that
> particular talk seemed to be concerned with what can be said about
> steady states, and a kind of “holographic” manner in which the
> dynamics either within or outside the boundary may be encoded in
> timeseries of states on the boundary (the Markov blanket).
I think this statement is the first time I've felt I penetrated this use
of "holographic"...  the dimensional compression as key rather than the
pervasive distribution.  As for my own understanding, I am used to
thinking in terms of the plenoptic function *with* phase.   I believe
that holographic in this context is a subdimensional (e.g. 2d
holographic plate) sampling of that field and the subsequent ability to
reconstruct a little (or a lot) about the entire full-dimensional
plenoptic field from that.    The Markov Blanket seems to be a nice
topological dual to the geometric (in holography).
>  In that respect, the idea seems similar to what the Chaos Cabal back
> at UCSC (Farmer, Packard, Shaw, Crutchfield) did with “geometry from a
> timeseries”, arguing, for example, that one could reconstruct aspects
> of spatial structure in a turbulent flowfield from samples of velocity
> at a single point in space, but over extended time.  It does seem that
> there would need to be some kind of trapping condition: that state
> information not be able to flow to infinity at finite rate forever, so
> that eventually any states however remote would get reflected back
> onto the (finite, by construction) boundary.
Thus the subdimensional sampling/collapse point above.   I think the
Chaos Cabal characterization of "geometry of timeseries" you bring up
here is related to SG's dual-field (meta) theory in formation?
>  I have not tried to think carefully about what kinds of information
> capacity limits should be needed for that to be possible, and it isn’t
> something I have ever studied from those who may know a lot about
> those questions.  The notion of finiteness and “reflecting back” seems
> similar to me, to the way total internal reflection operates in
> Anderson localization.  I don’t know what-all has been done to make
> mappings between information dynamics on Boolean networks, and
> continuum or peudocontinuum systems such as Anderson-localizing
> insulators.
Wow!  Half a dozen ideas/references triggered here...  
topological/continuum duals...
> I found Karl’s talk a bit frustrating; it did not have the feel of a
> talk that was mostly concerned with presenting a tool and putting it
> in the listener’s hand to understand and use.  It was again the
> firehose, with a sort of faux-bashful admission at the beginning that
> he always tries to put everything he knows into every talk, and will
> therefore not finish the narrative he starts.  Too many strings of
> notation without explaining how the reader should know what idea it
> was after or how that was reflected in the notation.  Having also
> committed that laziness in talks, I am in no position to throw stones,
> but listening to Karl makes me want to be more conscientious the next
> time I have to present something.
Is such a "lazy talk" not also "holographic" in the sense that the full
complexity of the ideas is projected onto a set of slides and a verbal
narrative (and a few gesticulations) for the "receiver" to reconstruct
some subset?
> But maybe it’s all okay.  It may be that what he is doing establishes
> a useful kind of holography principle, mapping currents and state
> fluctuation statistics from a volume (which could perhaps be
> indefinitely large) back onto the finite boundaries of interiors in
> that volume.  If indeed the whole state space is infinite, but the
> information dynamics is trapping, then there should be some kind of
> large-deviation behavior, such as occurs in reliable coding theory,
> talking about how more remote volumes, carrying ever-less probability
> to be occupied, will take longer and longer to have their
> contributions to fluctuations in the overall state reflected back onto
> any finite boundary in the interior.
This equivalence-of/interchangeability-with a hyper-volume to a finite
boundary (rather than a planar or similar, non-bounding) subdimensional
is the crux (I think) of what i've been ignoring in the "holographic"
metaphor in this context.   I was being (overly) literal... somehow the
complement to or contradiction-of Glen's accusation of excess meaning in
metaphors?  Maybe my overly *literal* binding *is* excess meaning in the
mapping, though I started this stream-of-consciousness with it as a
poverty-of-meaning (i.e.  a non-closed surface when a bounded surface
was required?)
>
> Any results of that kind, however, would probably be available only
> for steady states.  Dynamics would offer a variety of cases growing
> exponentially in the volume, and I don’t see how they could ever be
> tamed by projection onto a finite interior surface.  As far as I could
> tell, be only discussed the steady-state case in his talk.
This is an open (in my mind) question which I look forward to hearing
more elaboration of in this forum.
>
> Sorry I do not know how to answer anything of substance.  It would
> take a long slog through a lot of reading.  Maybe someday….  I
> wouldn’t want to discourage somebody else from doing it.
Useful to me, even if my "reflection" of what I heard here might sound
like incoherent noise.... I had to write it, even if I might not
actually hit <send> before I hit <delete>
>
> Eric