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Re: [ontolog-forum] ontolog-forum Digest, Vol 154, Issue 38

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Date: Fri, 16 Oct 2015 15:58:11 +0100
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Today's Topics:    (06)

   1. Re: Software Engineering Ontology of a Robot Finger? (Rich Cooper)
   2. Re: A Question About Logic (Pat Hayes)    (07)

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Message: 1
Date: Thu, 15 Oct 2015 18:15:47 -0700
From: "Rich Cooper" <metasemantics@xxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [ontolog-forum] Software Engineering Ontology of a Robot
To: "'[ontolog-forum] '" <ontolog-forum@xxxxxxxxxxxxxxxx>,      "'Thomas
        Johnston'" <tmj44p@xxxxxxx>
Message-ID: <020401d107b0$30a2f700$91e8e500$@com>
Content-Type: text/plain; charset="utf-8"    (09)

I found an article on a robot finger at the Kurzweil site:    (010)

http://www.kurzweilai.net/a-realistic-bio-inspired-robotic-finger    (011)

A realistic bio-inspired robotic finger    (012)

Initial use is in underwater robotics     (013)

October 9, 2015    (014)

http://www.kurzweilai.net/images/Bio-Inspired-Robotic-Finger.jpg    (015)

Heating and cooling a 3D-printed shape memory alloy to operate a robotic
finger (credit: Florida Atlantic University/Bioinspiration & Biomimetics)    (016)

The photos seem very realistic, though a little better sculpting of the
casts might make it more so.  But what do you do with a robotic finger?    (017)

Here is an interoperability challenge for those who want to understand the
software engineering implications of a strange new development.  What would
you encode into the objects, instances, methods, events, etc of an ontology
that fully describes and in no way limits the finger and its subcomponents?    (018)

What use cases do you foresee the finger participating in?    (019)

Can you enumerate all the ways in which the finger instances will be used in
the future?    (020)

I am thinking of a very valuable use case, so the test will be whether you
predict my use case.      (021)

Sincerely,    (022)

Rich Cooper,    (023)

Rich Cooper,    (024)

Chief Technology Officer,    (025)

MetaSemantics Corporation    (026)

MetaSemantics AT EnglishLogicKernel DOT com    (027)

( 9 4 9 ) 5 2 5-5 7 1 2    (028)

http://www.EnglishLogicKernel.com     (029)

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Message: 2
Date: Fri, 16 Oct 2015 02:04:44 -0500
From: Pat Hayes <phayes@xxxxxxx>
Subject: Re: [ontolog-forum] A Question About Logic
To: Thomas Johnston <tmj44p@xxxxxxx>
Cc: "\[ontolog-forum\]" <ontolog-forum@xxxxxxxxxxxxxxxx>
Message-ID: <A07C17D3-8D8F-4D26-A54A-4C151B33F0FF@xxxxxxx>
Content-Type: text/plain; charset="utf-8"    (032)

On Oct 15, 2015, at 4:14 PM, Thomas Johnston <tmj44p@xxxxxxx> wrote:    (033)

> Oct 15, 2015.
> Tom and Pat 1
> Original intuition. If I say "Some dogs are friendly", and then later
change my mind and say "No dogs are friendly", I'm talking about dogs, in
both cases. If I believe that there are dogs when I say that some of them
are friendly, I continue to believe in dogs when I change my mind and say
that none of them, or perhaps that all of them, are.    (034)

FWIW, I entirely agree with your intuition in this particular example, but
the point that you seem to miss is that this cannot be due to the logical
structure of these sentences, because other examples with exactly the same
logical form do not support that intuition. To see this, just exchange the
property 'friendly' for something vacuously true of all things. For example:
"Some dogs are real", which is another way to say "Some dogs exist", changes
its mind to give "No dogs are real", ie no dogs exist. To emphasize: this
has exactly the same logical form as your case, but supports a different
I am concerned by this counter-example.  Isn't Kant's refutation of the
ontological argument ('existence is not a predicate') relevant her?
Statements of the form 'some dogs are real', 'some dogs are not imaginary',
'some dogs have the property of existence' all purport to ascribe a property
to dogs, whereas they are really statements of existence which can be
negated.  Any real property ascribed to a dog (e.g. 'some dogs are
friendly') when negated would continue to support the intuition of
Our shared intuition in the dog example arises from the knowledge that we
both share that something can fail to be friendly and still be a dog, ie
that Ex. Dx & ~Fx. But that is another fact about the world, not expressed
in the original sentence and not entailed by it.     (035)

> It is not part of predicate logic to force me to say something I don't
believe.    (036)

Of course not.     (037)

> Tom and Pat ? a Counter-Intuition
> My Own Counter-Intuition. On the other hand, my intuition also tells 
> me that "No dogs are friendly" can be paraphrases as "Nothing is both 
> a dog and is friendly". And this statement will obviously be true even 
> if there are no dogs. In which case, we must express that statement as 
> a hypothetical, i.e., in a form which does not say "There is", or 
> "There exists". This intuition says that the negation of "Some dogs 
> are friendly" can indeed be expressed without ontological commitment, 
> as: Ux(Dx --> ~Fx), (or, BTW, as (Ux(Fx --> ~Dx).)
> If we express the negation of "Some dogs are friendly" this way, negation
has caused us to switch from being committed to the existence of dogs, to
dropping that commitment.    (038)

As, it seems obvious to me, it should. If a sentence S expresses a
committment, then its denial ~S should deny that committment, not repeat it.    (039)

> So if I can't find another way to express the negation of "Some dogs are
friendly", then I need to drop my original intuition and all this will have
been just a tempest in a teapot.
> So here's my attempt to formalize the negation of "Some dogs are friendly"
without switching from conjunction to material conditionals. I begin by
using this paraphrase: "No dogs are friendly". I'm talking about dogs, just
as I was when I said "Some dogs are friendly". From this point of view,
"Nothing is both a dog and is friendly" is not synonymous with "No dogs are
friendly".    (040)

Hmm. But surely there are entailments between these. Do you agree that 'no
dogs are friendly' certainly at least entails 'nothing is both a dog and is
friendly' ? This seems intuitively clear to me, for the latter would be
false only if there were a friendly dog. Similar reasoning shows that the
reverse entailment also holds: for if nothing is both doggish and friendly,
then a friendly dog is clearly impossible. So these two statements entail
each other, which means that they have identical truth conditions (they are
true or false in exactly the same circumstances: they make identical claims
about the world.) So how can you believe one of them but not the other?    (041)

> The former is an awkward paraphrase whose purpose is to support a view of
universal quantification in which it does not involve ontological
commitment. The latter is a way to talk about all dogs, not just about some
of them.    (042)

But if it talks about all dogs, then surely its logical form should be
something like 'all dogs....', which is standardly rendered as 'forall
things x, if x is a dog then....'. Again, this seems kind of obvious. Which
part of it do you think is mistaken? (Do you object to the standard
rendering of a restricted quantifier ('all dogs...') as a universal
implication (Ux Dx -> ...) ?)    (043)

> So here's my attempt.
> Tom and Pat 3
> Tom: <<<Why should "All dogs are renates" not be expressed as Ux(Dx & 
> Rx)?>>>
> Pat: <<<Because that would then also express "All renates are dogs", 
> by the symmetry of conjunction, and would entail "Everything is a 
> dog", by &-elimination.>>>
> Tom: I hadn't thought of that. But the following occurs to me:
> Statements have a subject and a predicate. Considering atomic statements,
to keep things simple. So "All dogs are renates" has "dogs" as its subject
term (aka "NP") and "are renates" as its predicate term (aka "VP").    (044)

? Are you saying that the logical form of this should be Renates(Dogs) ? (I
hope not)    (045)

> NPs identify types, i.e. universals whose instances are particulars. VPs
identify properties/relations, i.e. universals whose instances are not
particulars. Particulars (Aristotelian primary substances) exist without
dependency on properties; but properties depend on particulars to "inhere
in".    (046)

This seems very shaky ground on which to try to build a theory. In English,
at least, nominalizations allow almost any verb to be treated as a noun. If
the verb "shake" must identify a non-particular universal, what does the NP
"a shaking" denote? Is not every shaking an instance of the verb 'to shake'?    (047)

> Predicate logic ignores this distinction.    (048)

Because it plays no role in assigning truth-conditions of sentences.     (049)

> Dx and Fx, in my examples, are treated the same; both are predications.
> Now suppose that this distinction between instances of types and 
> instances of properties is important enough to bring in to our 
> formalisms. Let's use the subscripts "T" and "P" to make the 
> distinction. Then
> "All dogs are renates" would be expressed as Ux(Dtx & RPx).
And-elimination would ruled out for cases like these.    (050)

Why? &-elimination is an inference rule which applies to any conjunctive
sentence, regardless of the nature of the conjuncts. The semantic
justitification for this rule comes from the truth-conditions for the
connective, which are not changed by tinkering with the details of its
component sentences.     (051)

AFAIKS, nothing is changed by your proposed distinction and its subscripted
syntax. Both kinds of atomic sentence are still atomic sentences, and have
truth-values just as before, indeeed exactly the same truth values that they
had before we made this distinction. So the actual *logic* will proceed in
exactly the same way after this change as it did before the change.     (052)

> Standard boolean operators would be restricted to working on property
predications only.    (053)

What could possibly justify such a restriction, and in any case what does it
even mean? Your example sentence, which conjoins a property and a type
predication, violates this restriction. Does it itself not have truth
conditions?     (054)

> Doing predicate logic like this, the existential quantifier over type 
> predications would say that an individual of the stated type exists. 
> The universal quantifier would say that all individuals of the stated 
> type exist    (055)

Why would the meaning of the universal quantifier be changed to that of an
existential? And what do you mean by the 'stated type'? The body of a
universal sentence might have any form: it need not be restricted to simple
syllogistic forms like 'all swans are white'. What would we make of a
sentence like Ux Uy ( (Tx & Ty & Bxy) ->  Ez (Iz & Szx & Fzy) ) for example,
which by the way is one axiom of a simple temporal ontology.    (056)

> which, if there are any such individuals, is a tautology.    (057)

(Aside. Well, no. A tautology is *logically* true, ie true in *all*
interpretations.)    (058)

>  But now both existential and universal quantification carry ontological
> So how would we deny existence? Well, for example, to say "There are no
dogs", we would write: Ux(~Dtx). This says that nothing in our universe of
discourse is of type; in other words, that there are no dogs.    (059)

But if the universal quantiifer asserts universal existence of the type,
then why is this not a logical contradiction?     (060)

> What if we wrote: Ex(~Dtx). What would that say? It would say that there
is at least one thing in our universe of discourse which does exist and is
not a dog, i.e. which is not an instance of the type D.    (061)

These are exactly what these sentences mean already, so I fail to see how
you can preserve these meanings with your proposed change to the meaning of
the universal quantifier.     (062)

I do not think that you have a coherent logic defined here yet.     (063)

> I think this suggestion has two things going for it.    (064)

It is not yet stated in enough detail to be treated as a suggestion. I
honestly think that you will not be able to make it into a coherent
suggestion without it being equivlaent to conventional predicate logic. This
space has been very thoroughly explored already.    (065)

> First, when talking about anything, switching from "Some" statements to
"All" statements doesn't change ontological commitment. In both cases, if
negation isn't used, I'm talking about what I presume exists. If I want to
say that nothing of a specific type exists, say dogs, I write: Ux(~Dtx). If
my switch involves the deMorgan's equivalence of "Some" to "Not All Not" and
"All" to "Not Some Not", I still don't drop, or pick up, ontological
> The second thing this has going for it is that it introduces into
predicate logic an important distinction that, to date, predicate logic does
not represent, and never has: the distinction between universals (types)
whose instances are particulars (Aristotelian primary substances, as I
explain in Ch. 5 of BDTP), and universals whose instances are properties of
particulars or relations between particulars. This distinction is at the
heart of language. Atomic statements pick something out by identifying what
type of thing it is, and then saying something about it, which amounts to
ascribing a property or relationship to it.    (066)

I really have no idea what you are talking about here, but it sounds like a
version of sorted FOPC with restricted quantiifers might provide the
analysis you are seeking. So instead of - I will use CLIF lisp-style
notation for clarity -     (067)

(forall (x)((P x) implies foo)     (068)

one writes     (069)

(forall ((x P)) foo),     (070)

ie 'forall x of type P, foo'    (071)

> One thing against this proposal is that it isn't worked out, and there
would be a lot of working out to do. How would proofs (inferences) work in
this kind of FOPL?    (072)

I would suggest starting with a semantics, and try to state truth conditions
on sentences, and show how they differ from the conventional ones.     (073)

Pat    (074)

> How would they work in modal predicate logics? Truth be told, I have no
idea and I lack the expertise to try to answer these questions. It may be
that we have the predicate logic we do because trained logicians have gone
down this path some ways farther than I have ? far enough to find out that
it's a blind alley.
> I'll try to respond to some of your other comments soon. In the meantime,
if you don't think anything is to be gained by continuing this conversation,
I'll understand completely.
> Thanks for working so hard to help me understand why predicate logic is as
it is.
> Tom
> On Tuesday, October 13, 2015 9:04 PM, Pat Hayes <phayes@xxxxxxx> wrote:
> On Oct 13, 2015, at 10:53 AM, Thomas Johnston <tmj44p@xxxxxxx> wrote:
> > Oct 13, 2017.
> > 
> > My intuitions tell me that anyone who asserts "All dogs are renates"
believes that there are dogs (i.e. is ontologically committed to the
existence of dogs) just as much as someone who asserts "Some dogs are
> I think your intuition needs some pumping with more examples. Try these:
> All unicorns are imaginary.
> All large unicorns are male.
> All composite prime numbers are larger than 13.
> Your intuition has some very strange consequences. You claim that  (Ux Px
-> Qx)  entails (Ex Px). But the first is equivalent to (Ux. ~Qx -> ~Px), so
it must also entail (Ex ~Qx) So "All dogs are renates" entails the existence
of some non-renates. But if so, then "All dogs are real entities" (or some
other vacuously true property in place of Q), must entail that some non-real
entities exist, which is false. So we can derive a falsehood (perhaps
necessarily false) from a truth (perhaps a necessary truth), using your
intuitions as a guide.  
> > Suppose someone else asserts, instead, that "No dogs are renates". 
> > Certainly, to do that, that person must believe that there are such 
> > things as dogs
> ?? Of course not.  For example:  "No blue rainbows have gold highlights."
Which, by the way, I believe and am quite sure is true, precisely *because*
there are no blue rainbows. Or, a more realistic example, one that actually
does arise in some conversations here in the deep south, "No spirit guide
will cause you harm."
> > and, in addition, believe that some of them are not renates (a false
belief, of course).
> > 
> > Now for "Some dogs are friendly", and also "Some dogs are not friendly".
In both cases, we all seem to agree, someone making those assertions
believes that there are dogs.
> > 
> > Now I'm quite happy about all this. If I make a Gricean-rule serious
assertion by using either the "All" quantification or the "Some"
quantification, I'm talking about whatever is the subject term in those
quantifications ? dogs in this case. I'm particularly happy that negation,
as it appears in the deMorgan's translations between "All" statements and
"Some" statements, doesn't claim that a pair of statements are semantically
equivalent, in which one of the pair expresses a belief that dogs exist but
the other does not.
> > 
> > But in the standard interpretation of predicate logic, that is the
interpretation. In the standard interpretation, negating a statement creates
or removes the expression of a belief that something exists.
> Well, negating the statement expressing that belief yields another
statement denying that belief. Why would anyone expect otherwise? Surely
that is the whole point of negation, that not-P expresses the exact opposite
of what is expressed by P, so they cannot both be true. 
> > My beliefs in what exist can't be changed by the use of the negation
> So if you say "Foos exist", and I respond, disagreeing with you, "There
are no foos", then we are in fact agreeing with one another! Do you really
find this a reasonable interpretation?  If you do, then what could I
possibly say, in order to disagree with you about such a claim of existence?    (075)

> >  Apparently, John's beliefs can, and so too for everyone else who feels
comfortable with predicate logic as a formalization of commonsense
reasoning, and with the interpretation of one of its operators as "There
exists ....".
> > 
> > I usually don't like getting into tit for tats. Those kinds of
discussions always are about trees, and take attention away from the forest.
But I'll make exceptions when I think it's worth taking that risk (as I did
in my response to Ed last night).
> > 
> > So:
> > 
> > From John Sowa's Oct 12th response:
> > <<<
> > TJ
> > > why, in the formalization of predicate logic, was it decided that 
> > > "Some X" would carry ontological commitment
> > 
> > Nobody made that decision.  It's a fact of perception. 
> I wish John had not mentioned perception here, as it muddies the
discussion with irrelevant ideas. It is not a fact of perception. but a fact
of the truth-conditions of the sentences involved. You may cite medieval
scholars as much as you like, but I would be more impressed by a brief
account of what you take the truth-conditions of a sentence of the form (Ux
Px -> Qx) to actually be, and show us how this will entail Ex Px. 
> >  Every
> > observation can always be described with just two operators:
> > existential quantifier and conjunction. No other operators can be 
> > observed. They can only be inferred.
> > >>>
> > (1) If all ontological commitments have to be based on direct
observation, then we're right back to the Vienna Circle and A. J. Ayer.
> > 
> > (2) And what is it that we directly observe? A dog in front of me? Dogs,
as Quine once pointed out, are ontological posits on a par with the Greek
gods, or with disease-causing demons. (I am aware that this point, in
particular, will likely serve to reinforce the belief, on the part of many
engineering types in this forum, that philosophy has nothing to do with
ontology engineering. That's something I want to discuss in a
"contextualizing discussion" I want to have before I pester the members of
this forum with questions and hypotheses about cognitive/diachronic
semantics. What does talk like that have to do with building real-world
ontologies in ontology tools, in OWL/RDF ? ontologies that actually do
something useful in the world?
> > 
> > (3) I wouldn't talk about some dogs unless I believed that some dogs
> Suppose you believe that dogs do not exist, ie that there are no dogs. And
you wish to say this to someone, perhaps to enlighten them about the true
nature of their animal pet. What will you say? You have to say something
like "There are no dogs", or "Nothing is a dog". Rendered into logic, you
have to say Ux.~Dx  or ~Ex.Dx. Either way, you have to talk about dogs, in
order to deny their existence. So someone might well want to talk about dogs
- perhaps it would be better to say, to use dog language - when they do not
believe that dogs exist. 
> > And if some dogs exist, then all dogs do, too.
> Clearly this is false. I had a dog once, called Sally. Sally existed. On
the other hand, the Hound of the Baskervilles was an imaginary dog. That dog
did not exist. Similarly Rin-Tin-Tin was a fictional dog that did not exist.    (076)

> > Either there are dogs, or there aren't. If there are, then I can talk
about some of them, or about all of them. If there aren't, then unless I am
explicitly talking about non-existent things, I can't talk about some of
them nor can I talk about all of them, for the simple reason that none of
them exist. To repeat myself: if any of them exist, then all of them do.
> > 
> > (4) And I am, of course, completely aware that trained logicians since
Frege have been using predicate logic, and that, at least since deMorgan,
have been importing to negation the power to create and remove ontological
> > 
> > (5) Here's a quote from Paul Vincent Spade (very important guy in
medieval logic and semantics):
> > 
> > "This doctrine of ?existential import? has taken a lot of silly abuse in
the twentieth century. As you may know, the modern reading of universal
affirmatives construes them as quantified material conditionals. Thus ?Every
S is P? becomes (x)(Sx ? Px), and is true, not false, if there are no S?s.
Hence (x)(Sx ? Px) does not imply (?x)(Sx). And that is somehow supposed to
show the failure of existential import. But it doesn?t show anything of the
sort .... "
> > http://pvspade.com/Logic/docs/Thoughts,%20Words%20and%20Things1_2.pd
> > f
> It is worth reading the rest of that footnote. He agrees that  (x)(Sx ?
Px) does not imply (?x)(Sx), but points out that (Ux)(Px) implies (Ex)(Px),
and that *this* is the real existential import of modern logic. 
> "The modern equivalent of existential import, therefore, is not: (x)(Sx ?
Px) ? (?x)(Sx), but rather (x)(Px) ? (?x)(Px). And that holds in standard
modern logic, which is therefore just as much committed to existential
import as traditional logic is."
> Perfectly correct, but has no bearing on the issue you are raising here. 
> > 
> > So Spade approaches this as the issue of the existential import of
universally quantified statements. He points out that, from Ux(Dx --> Rx),
we cannot infer Ex(Dx & Rx). The rest of the passage attempts to explain
why. I still either don't understand his argument, or I'm not convinced by
it. Why should "All dogs are renates" not be expressed as Ux(Dx & Rx)?
> Because that would then also express "All renates are dogs", by the
symmetry of conjunction, and would entail "Everything is a dog", by
> Best wishes
> Pat Hayes
> PS there is a wonderful extended essay here on this general topic:  
> http://plato.stanford.edu/entries/ontological-commitment/
> > From John's reply, I think he would say that it's because we can only
observe particular things; we can't observe all things. But in the preceding
points, I've tried to say why I don't find that convincing.
> > 
> > (6) Simply the fact that decades of logicians have not raised the
concerns I have raised strongly suggests that I am mistaken, and need to
think more clearly about logic and ontological commitment. But there is
something that might make one hesitate to jump right to that conclusion.
It's Kripke's position on analytic a posteriori statements (which I have
difficulty distinguishing from Kant's synthetic a priori statements,
actually -- providing we assume that the metaphors of "analytic" as finding
that one thing is "contained in" another thing, and of "synthetic" as
bringing together two things first experienced as distinct, are just
metaphors, and don't work as solid explanations).
> > 
> > All analytic statements are "All" statements, not "Some" statements.
Kripke suggests that the statement "Water is H2O" is analytic but a
posteriori. In general, that "natural kind" statements are all of this sort.
Well, a posteriori statements are ones verified by experience, and so that
would take care of John's Peircean point that only "Some" statements are
grounded in what we experience.
> > 
> > I don't know how solid this line of thought is. But if there is
something to it, that might suggest that if we accept Kripke's whole
referential semantics / rigid designator / natural kinds ideas (cf. Putnam's
twin earth thought experiment also), then perhaps we should rethink the
traditional metalogical interpretation of "All dogs are renates" as Ux(Dx
--> Rx), and consider, instead, Ux(Dx & Rx).
> > 
> > Well, two summing-up points. The first is that Paul Vincent Spade thinks
that my position is "silly", and John Sowa thinks that it's at least wrong.
The second is that such discussions do indeed take us beyond the concerns of
ontology engineers, who just want to get on with building working
> > 
> > As I said above, I will address those concerns of ontology engineers
before I begin discussing cognitive semantics in this Ontolog (Ontology +
Logic) forum.
> > 
> > Regards to all,
> > 
> > Tom
> > 
> > 
> > 
> > 
> > 
> > On Monday, October 12, 2015 10:49 PM, John F Sowa <sowa@xxxxxxxxxxx>
> > 
> > 
> > Tom, Ed, Leo, Paul, Henson,
> > 
> > TJ
> > > why, in the formalization of predicate logic, was it decided that 
> > > "Some X" would carry ontological commitment
> > 
> > Nobody made that decision.  It's a fact of perception.  Every 
> > observation can always be described with just two operators:
> > existential quantifier and conjunction. No other operators can be 
> > observed. They can only be inferred.
> > 
> > EJB
> > > I was taught formal logic as a mathematical discipline, not a 
> > > philosophical discipline. I do not believe that mathematics has 
> > > any interest in ontological commitment.
> > 
> > That's true.  And most of the people who developed formal logic in 
> > the 20th c were mathematicians.  They didn't worry about the source 
> > or reliability of the starting axioms.
> > 
> > Leo
> > > most ontologists of the realist persuasion will argue that there 
> > > are no negated/negative ontological things.
> > 
> > Whatever their persuasion, nobody can observe a negation.  It's 
> > always an inference or an assumption.
> > 
> > PT
> > > on the inadequacy of mathematical logic for reasoning about the 
> > > real world, see Veatch, "Intentional Logic: a logic based on 
> > > philosophical realism".
> > 
> > Many different logics can be and have been formalized for various 
> > purposes.  They may have different ontological commitments built in, 
> > but the distinction of what is observed or inferred is critical.
> > 
> > HG
> > > I keep wondering if this forum has anything useful to offer the 
> > > science and engineering community.
> > 
> > C. S. Peirce was deeply involved in experimental physics and 
> > engineering.  He was also employed as an associate editor of the 
> > _Century Dictionary_, for which he wrote, revised, or edited over
> > 16,000 definitions.  My comments below are based on CSP's writings:
> > 
> >  1. Any sensory perception is evidence that something exists;
> >    a simultaneous perception of something A and something B
> >    is evidence for (Ex)(Ey)(A(x) & B(y)).
> > 
> >  2. Evidence for other operators must *always* be an inference:
> > 
> >    (a) Failure to observe P(x) does not mean there is no P.
> > 
> >        Example:  "There is no hippopotamus in this room"
> >        can only be inferred iff you have failed to observe
> >        a hippo and know that it is big enough that you would
> >        certainly have noticed one if it were present.
> > 
> >    (b) (p or q) cannot be directly observed.  But you might infer
> >        that a particular observation (e.g. "the room is lighted")
> >        could be the result of two or more sources.
> > 
> >    (c) (p implies q) cannot be observed, as Hume discussed at length.
> > 
> >    (d) a universal quantifier can never be observed.  No matter
> >        how many examples of P(x) you see, you can never know that
> >        you've seen them all (unless you have other information
> >        that guarantees you have seen them all).
> > 
> > TJ
> > > But now notice something: negation creates and removes ontological 
> > > commitment. And this seems really strange. Why should negation do
> > 
> > The commitment is derived from the same background knowledge that 
> > enabled you to assert (or prevented you from asserting) the negation.
> > 
> > > I'd also like to know if there are formal logics which do not 
> > > impute this extravagant power of ontological commitment / 
> > > de-commitment to the negation operator in predicate logics.
> > 
> > Most formal logicians don't think about these issues -- for the 
> > simple reason that most of them are mathematicians.  They don't 
> > think about observation and evidence.
> > 
> > CSP realized the problematical issues with negation, but he also 
> > knew that he needed to assume at least one additional operator.
> > And negation was the simplest of the lot.  Those are the three he 
> > assumed for his existential graphs.  (But he later added 
> > metalanguage, modality, and three values -- T, F, and Unknown.)
> > 
> > John
> > 
> > PS:  The example "There is no hippopotamus in this room" came from a 
> > remark by Bertrand Russell that he couldn't convince Wittgenstein 
> > that there was no hippopotamus in the room.  Russell didn't go into 
> > any detail, but I suspect that Ludwig W. was trying to explain the 
> > point that a negation cannot be observed.
> > 
> > 
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