Hi @AndriusKulikauskas,

Apologies for the delay in my reply. I have not been frequenting this forum of late. If you tag me e.g. @ChrisGoddard, I should get an email notification though.

>Chris Goddard, I saw your comment and your link to your recent paper, A map of a research programme for subtlety theory. At Research Gate, I also found your book, A treatise on information geometry. and your papers on game theory.

Thank you for your interest in my work.

>Would you like to exchange ideas related to subtlety theory and information theory? I am curious how you look at these subjects. Perhaps we have overlapping interests. Could would explore them here?

Certainly, I would certainly be interested in exploring the possibility of dialogue.

>I noticed that in your paper on subtlety theory you mention Roy Frieden's book, [Physics from Fisher Information](catdir.loc.gov/catdir/samples/cam032/98020461.pdf).
>
>I read [a blogger's skeptical review of Frieden's book](http://bactra.org/reviews/physics-from-fisher-info/). Perhaps you might address those criticisms from your own perspective. [...]

There have been a number of parties who have written critically about Roy Frieden's work. One notable example of this is a more detailed critique of Frieden's book [here](http://faculty.poly.edu/~jbain/physinfocomp/Readings/02LavisStreater.pdf) which is probably a bit more detailed in terms of its analysis of Frieden's ideas than the blog post you linked above. At the end of this article, D.A. Lavis and R.F. Streater end with the remark (emphasis mine):

>"We regret to say that we find this book to be fundamentally flawed in both its overall concept and mathematical detail. It cannot be read as a textbook providing a valid approach to physics. *However it could, perhaps, be a source of stimulation for some new and interesting work.*"

I would consider my research programme that builds on top of Roy Frieden's research programme as such a potentially "new and interesting work" which has been stimulated by Roy Frieden's work on the matter. In such a way my work is neither in conflict with the view of Lavis / Streater, nor of Frieden, but rather in a sense orthogonal to these other two parties.

In terms of the manner in which the polemic was written, I have little to comment, other than the fact that I think a little bit of humility and consideration can go a long way in general when commenting on the work of others. People should really try to build each other up in the sciences, rather than tear one another down.

Returning to the blog post you mentioned above - my key difficulty with Cosma's blog post is that it is written more from the perspective of the philosophy of physics, and therefore by its very nature is inherently woollier than simply analysing the actual mathematics of what Roy Frieden was doing. It is also not a paper, but a blog post, and therefore should not be read as a serious critique, in the same way that, say, a paper would be. Finally, I am not overly interested in philosophy of physics (although I can understand its value); rather I tend to be more interested in the "shut up and compute" philosophy as extolled I think by at least one prominent academic in recent memory.

>[...] Or, more importantly, to explain what you find compelling [...]

What I found compelling about Roy Frieden's work was that it provided a potential avenue to understanding how to derive hamiltonians for physics from first principles. Even if his approach was not thoroughly rigorous and mathematically watertight, I think from an intuitionistic perspective he was clearly onto something. That is what drew me to his research originally in 1999, and pulled me back after I had learned a bit more physics in 2004 and was about to start my doctoral studies.

Understanding where hamiltonians come from or having some idea as to a principle as to how to do so would be potentially extremely significant and a very powerful insight. Indeed, this was hammered home to me from my undergraduate and honours studies - it seemed to me that on the basis of 19th and 20th century physics that there was really no clear explanation or consensus as to where really action functionals came from, other than through the use of tried and tested heuristics and "physical intuition" based loosely on arguments of "symmetry". *(The latter of these - appeals to notions of symmetry - presumably relates to thinking of things in terms of Lie Groups that act on geometric models in which dynamics occurs, and in a way could potentially be made more rigorous in and of itself, however this was not an avenue of thought towards which my interests took me. Needless to say, however, I have my doubts that the existing machinery presents an acceptable level of generality.)*

From a mathematician's perspective, however, appealing vaguely to "physical intuition" and "symmetry" (in a primitive fashion) is not good enough - one would really like to be able to "derive" or "prove" that the equations of electromagnetism, general relativity, quantum mechanics etc can be derived from particular natural assumptions about the geometry in which dynamics is to take place. Frieden laid the groundwork there, and I'd like to think that I did a fair bit of work from 2005 to 2010 fleshing it out, and then from 2010 to 2020 in terms of generalising this framework.

>[...] , or simply to write more about your personal goals, in general.

My personal goals in terms of my research programme at present are to try to hand over a bit of what I've done. I think that this is reasonable, as I am no longer a young man, and am quite definitely middle-aged now. Also, I need a bit of a break from thinking about some of these things.

There are obviously threads of thought I'd like to potentially pick up again at some point, maybe in another three to five years or so, but I'm in no hurry to continue doing serious research at the moment; particularly since my paid work at present is as an engineer (which I enjoy tremendously, and have no real desire to change) rather than as an academic.

I have been attracted to this forum again really for two reasons:

* one, because there are top mathematicians and scientists who occasionally visit this forum or its loosely affiliated entity, the n-category cafe and the n-lab, who might be able to accept the messy bundle of insights that I've gathered piecemeal over the last 15 years, in a part-time fashion - and which is summarised as you mentioned in [this paper](https://www.researchgate.net/publication/338825550_A_map_of_a_research_programme_for_subtlety_theory),
* and two, because the ideas being taught here at present regarding functional programming with categories fit my current agenda of becoming a better programmer / software engineer - which is my current chosen vocation.

>[My motivation to learn more about the Fisher Information]

I have things to do now, but I haven't neglected to notice your last comment about your own research. I will draft and post another comment in the next day or so sharing my thoughts on same. Here though is a teaser - I am reminded from having a quick view of your own work of [Dave Snowden's Cynefin framework](https://en.wikipedia.org/wiki/Cynefin_framework).