Dear all, Thank you for mailing, throughout decades, as it has helped create new things and invite younger researchers, at the same time it preserves community and maintains a forum. I've learned a lot, and I am grateful for that. --- Yes, looking back, we have good memories, and we know we did the right things. Many things we wouldn't have done differently. Are we looking forward? What's in for CT in 50-100 years to come? I'm less than epsilon in the universe on CT knowledge but allow me to write this. --- I wrote recently to Michael Barr privately as I had found a mail exchange from 2015. On 2015-01-29 02:59, Michael Barr wrote: I wonder what kind of science outside of string theory would find CT useful. I wrote some, and related to what I have posted sometimes at CT (and FoM) on the need to use CT in understanding syntax within the foundations of logic. --- --- --- Here's what I (somewhat shortened) wrote to Michael: I have come back to that "outside of string theory". For decades I was flabbergasted about Gödel's fame given his 1931 paper. He is basically very shallow on formalising what formulas and provable formulas actually are. Once he has sets for these, no matter what they are, he sees formulas in there as sequences of symbols, and proofs as sequences of sequences of symbols. In his footnote 9 he says he works with an "isomorphic image" of Principia Mathematica. It could and should be an adjunction if he would have tried something out. Anyway, in Gödel's use of the power type, he essentially works with terms over sets rather than sets of terms, i.e.. he leans on the TP composition rather than the PT composition. So basically he doesn't realize that his substitutions cannot compose. His efforts on substitution is in his steps 30 and 31 in his 1-46 steps before he "proves" his incompleteness results. So basically Gödel proves incompleteness of systems that actually do not exist anywhere. Saying that whatever system P we have, formulas must be nothing but sequences of symbols (Peano 1889), and proofs are sequences of such sequences, is absurd. --- On 2015-01-29 02:59, Michael Barr wrote: I wonder what kind of science outside of string theory would find CT useful. Today I write: I wonder why CT never looked into being useful more generally within fuondations, and not just marginally curious about its own foundations. Gödel's meta language is "logical arithmetic" where his "numbers" and recursion reside, and he uses that to drag sequences of sequences of symbols into the mud. So I wonder why CT never looked into using categorical arithmetic as meta to enrich Hilbert's program. Gödel's 1931 paper is seen as having crashed everything about Hilbert's program, and he did it by dragging sequences of sequences of symbols into the mud. --- The Foundations of Mathematics side never seriously looked into CT, and CT never seriously looked into FoM. I always wondered why. --- --- --- That was indeed my mail to Michael a few days ago. To repeat: Are we looking forward? What's in for CT in 50-100 years to come? Some 50 years ago Bernays and Gödel exchanged letters on category theory. They had heard something about someone being in Poland, but that was basically it. Today, is there any exchange at all between CT and FoM (not the mailing lists!)? --- Thank you Bob Rosebrugh for everything you've done, and thank you JS Lemay in advance for everything you will do. Best, Patrik On 2023-10-26 17:14, Bob Rosebrugh wrote:
Dear Colleagues,
From March 1990 until recently it was my privilege to moderate the categories mailing list. For a couple of years it has been my intention to pass the list to a new moderator, but I was too slow to act. Changes to IT service at my former employer, Mount Allison University, abruptly made it impossible for me to continue running the list.
Those changes were unexpected for me, but I have been away from the campus for over three years and was not aware. The IT staff at Mount Allison have always been very supportive of the list and I thank them for their more than three decades of generous assistance.
It is a reassuring pleasure to know that the list is now in the capable hands of JS Lemay who kindly accepted the invitation to revive it. I am very grateful. Moreover, there is no one better suited to the role and our community is fortunate to have him moderating. I am also very happy that the new home of the list is Macquarie.
Best wishes to everyone. I am hoping to see many of you in the not distant future, Bob Rosebrugh
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