Vaughan Pratt | 1 Nov 18:44 2010

Communes paper, schismatic objects

A couple of things.  First, I neglected to mention that "Communes via 
Yoneda, from an Elementary Perspective," Fundamenta Informaticae 123 
(2010) 1–16, DOI 10.3233/FI-2010-315 is about to appear and won't be 
findable by Google just yet.  Those interested in seeing it sooner can 
find it on my site at

Second, as I said I wasn't passing judgment on the wisdom of avoiding 
the term "schzophrenic" but merely pointing out the associated cost, 
which needs to be balanced against the harm of any given word.

So I followed Tom's pointer

linking to a discussion of alternatives, which seemed inconclusive.  Sam 
(Staton?) made the point however that even if schizophrenia is not the 
appropriate word, schizo is the appropriate prefix, having derived from 
the Greek "split."

So it is the medical condition that is inappropriately named, namely as 
"split madness," with phrenitis and frenzy having a common origin.

With that in mind it occurred to me that "schismatic" might be a 
suitable alternative, as providing better continuity with the older 
terminology by coming from the same root schizo, but more honestly so 
than schizophrenia since in this case there really is a multiple 
personality, and moreover there's nothing insane about it.  (And it's a 
syllable shorter to boot.)
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Dusko Pavlovic | 1 Nov 21:37 2010

Re: "schizophrenic" reference

peter selinger tells me that i viciously attacked tom leinster. i would
like to apologize for that appearance. i do not know tom, and had no
intention to address his post more than any of the previous 200 posts
about terminology. tom's was just the one where i blew up. i am sorry,

and i guess maybe i should say sorry to all that i blew up.

but i still think that it is a pity, and curious, that the best minds of
category theory don't have better things to do but to generate volumes of
email about words.

before i disappear, let me add two things.

1) the meanings of words evolve away from their origins, just like bat's
wings and seal's flippers evolved away from their ancestors' legs. the
original meaning of the word "word" was "promise". but people are
ignorant, and the meaning changed. if people start using the word
"schizophrenic" to describe a type of shoes, or a sexual orientation ---
that will in due time become the meaning of that word. that is how
languages work, if you don't mind.

2) proscribing some words for reasons of political correctness is often
patronizing. let us protect the weak by using the name of their weakness
only very very carefully, and with a serious face. because we are
stronger, so we should protect them. (and also use the opportunity to tell
everyone else what to do.)

once upon a time, black people used to be called the n word by some white
people. and what did black people do? yes, they wrote many petitions to
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Pattinson, Dirk | 1 Nov 22:08 2010

Wessex Theory Seminar, Imperial College, Thu Nov 4

The next edition of the Wessex Theory Seminar, an informal seminar series on Computer Science Theory will
be held at the Department of Computing, Imperial College London

   on Thursday, 4th Nov 2010    
   in Room 343, Huxley Building, South Kensington Campus

from 13:15 onwards.

Wessex seminars are fairly informal, there is no need to register, and I'd like to extend a warm invitation
to everybody. I'm including the provisional programme:

13.15 Edmund Robinson: Functional Interpretations and Proof Mining
13.45 Peter Mosses: On bisimulation and modularity
14.15 Coffee Break
14.45 Ross Horne: Linked Data Algebra
15.30 Coffee Break
16.00 Achim Jung: The Hofmann-Mislove Theorem
17.00 Short Break
17.15 Jan Rutten: Exercises in coalgebra – a coinductive proof of Moessner's theorem

More details about the Wessex Seminar in general can be found on the web at:

and the details concerning this meeting are available via:

Please get back to me if there are any question.

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Todd Trimble | 2 Nov 00:52 2010

Re: Communes paper, schismatic objects

A couple of things related to recent comments on "schizophrenic".

Vaughan Pratt wrote, with regard to possible alternatives to "schizophrenic"

"So I followed Tom's pointer

linking to a discussion of alternatives, which seemed inconclusive.  Sam
(Staton?) made the point however that even if schizophrenia is not the
appropriate word, schizo is the appropriate prefix, having derived from
the Greek 'split'. "

Although the discussion at the nLab might appear inconclusive, in actual
fact a number of people at the nLab and n-Category Cafe seem to have
provisionally adopted "ambimorphic", which I coined with the intended
meaning, "having both forms". I actually feel that is very appropriate in
practice; for example, in classical Stone duality, it is not enough to say 
dualizing object 2 is "split" between being seen as a compact Hausdorff
space and as a Boolean algebra. It is both at once: a Boolean algebra
object in the category of compact Hausdorff spaces, and we need both
forms in the same body so that we can say hom_{CH}(-, 2) is a Boolean
algebra valued functor.

With regard to Dusko's recent comments: it's quite understandable that
"political correctness" and endless debates over terminology can become
tiresome. But I'm not sure "political correctness" is quite the angle from
which Tom's objection comes. At the Cafe he brought it up here:

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Alan Bundy | 2 Nov 15:47 2010

Fwd: Petition: Boole's House at Grenville Place]


 	John Power suggested I send this to you to distribute to the international
categories mailing list, if you think that is appropriate.


The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.

-------- Original Message --------

Oggetto: [CSP] Petition: Boole's House at Grenville Place
Data: Mon, 01 Nov 2010 19:05:54 +0000
Mittente: Barry O'Sullivan <b.osullivan <at>>
A: constraints <at>, csp <at>


First, I would like to apologise to those who receive this
message more than once.

Now to the point:

Earlier this month George Boole's house on Grenville Place
in Cork - where he wrote "An Investigation of the Laws of Thought"
in 1854 - suffered severe damage. I've established a petition to
seek support for any initiatives that can be undertaken to
repair/restore the building urgently. The purpose of the petition
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Robert Seely | 2 Nov 17:27 2010

The higher order chain rule (categorically)

We'd like to announce our paper "The Faa di Bruno construction",
by J.R.B. Cockett and R.A.G. Seely,
a preprint copy of which may be found here:


In the context of Cartesian differential categories [BCS 09], the
structure of the first-order chain rule gives rise to a fibration, the
"bundle category".  In the present paper we generalise this to the
higher-order chain rule (originally developed in the traditional
setting by Faa di Bruno in the nineteenth century); given any Cartesian
differential category X, there is a "higher-order chain rule
fibration" Faa(X) -> X over it. In fact, Faa is a comonad (over the
category of Cartesian left (semi-)additive categories). Our main
theorem is that the coalgebras for this comonad are precisely the
Cartesian differential categories.  In a sense, this result affirms
the "correctness" of the notion of Cartesian differential categories.

[BCS 09] R.F. Blute, J.R.B. Cockett, R.A.G. Seely.
"Cartesian differential categories".
Theory and Applications of Categories 22 (2009), 622-672.


<rags <at>>

[For admin and other information see: ]
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Eduardo Ochs | 3 Nov 01:41 2010

Internal Diagrams in Category Theory


I think that following preprint might be of interest to some
people on the list:

   Title: Internal Diagrams in Category Theory
   Abstract: We can regard operations that discard information, like
     specializing to a particular case or dropping the intermediate
     steps of a proof, as _projections_, and operations that
     reconstruct information as _liftings_. By working with several
     projections in parallel we can make sense of statements like
     "$\Set$ is the archetypal Cartesian Closed Category", which means
     that proofs about CCCs can be done in the "archetypal language"
     and then lifted to proofs in the general setting. The method works
     even when our archetypal language is diagrammatical, has potential
     ambiguities, is not completely formalized, and does not have
     semantics for all terms. We illustrate the method with an example
     from hyperdoctrines and another from synthetic differential

It is at:

Best wishes to all,
   Eduardo Ochs
   eduardoochs <at>

[For admin and other information see: ]

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Tom Leinster | 3 Nov 03:56 2010

Re: "schizophrenic" reference

On Mon, 1 Nov 2010, Dusko Pavlovic wrote:

> tom's was just the one where i blew up. i am sorry, tom.

No problem.

I understand that posts about terminology get tedious, but I do actually
think this matters.  Mental health organizations constantly have to fight
misconceptions about mental illness.  Those misconceptions can do real
harm to those who are ill.  Schizophrenia as "split personality" is one of
them.  For example, Mind, a well-known British mental health charity,

     There is more media misinformation about schizophrenia than about any
     other psychiatric diagnosis.  It's not true that schizophrenia means
     'split personality'

Many websites on mental health contain statements along similar lines; a
few links are below.

We have the freedom to choose any term we like for the mathematical
concept.  We can do a small good thing by not choosing a term that
perpetuates a damaging myth about a serious psychiatric disorder.

Best wishes,

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Posina Venkata Rayudu | 3 Nov 14:31 2010

concept & truth-value

   Dear All,

Sentences, which are put together from words embodying concepts
[according to the laws of Grammar], can be true or false, but parts of
sentences i.e. words (e.g. of) can not be assigned a truth-value.

I'd appreciate very much any clarification or explanation of the above
observation, which many of you may also have made and thought about it
and worked on it.

I thought of sending this questions to catlist in part because I found
that similar observations are often made by those working in category
theory and those working in cognitive science. For example, Prof.
Lawvere in his 'Foundations and Applications' paper points out that it
is 'incorrect to think that concepts can be adequately characterized in
terms of properties alone.' As if echoing Lawvere, Smith and Medin also
draw our attention to the empirical finding that 'just listing
properties does not completely specify the knowledge represented in a
concept. People also know about the relations between the properties.'

Lawvere, F. W. (2003). Foundation and Applications: Axiomatization and
Education. The Bulletin of Symbolic Logic 9, p. 220.
Smith, E. E., and Medin, D. L. (1981). Categories and Concepts.
Cambridge, MA: Harvard University Press, p. 83.

Thanking you,
Sincerely yours,

[For admin and other information see: ]
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Neil.Ghani | 3 Nov 15:50 2010

ScotCat 3 - Second Announcement

*** Scottish Category Theory Seminar
*** Third Meeting
*** Thursday 2nd December 2010, 2-5.30pm
*** University of Strathclyde, Scotland

We are pleased to announce the Third Scottish Category Theory Seminar. The
is open, and all are welcome to attend. We have three invited speakers as

   * Marcelo Fiore (University of Cambridge)
     On Higher Order Algebra

   * Bas Spitters (University of Nijmegen)
      Bohrification: Topos theory and quantum theory

   * Ieke Moerdijk  (Universiteit Utrecht)
      Operads and dendroidal sets

If you are interested in attending ScotCats 3, you may also be interested
in the following event hosted
by the MSP group at the University of Strathclyde

  * Benno van den Berg
    A Crash Course on Algebraic Set Theory
    Morning of Friday Dec 3
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