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Very brief explanation of what modal logic gives us, and what
Original (from "The Tell-Tale Heart" by Edgar Allan Poe):


'possible worlds' means. Then at the bottom, why [[jbocre: Jordan DeLong|Jordan DeLong]]
The officers were satisfied. My _manner_ had convinced them. I


now think [[jbocre: mu'ei|mu'ei]] (and the related cmavo [[jbocre: ba'oi|ba'oi]] and such) is in
was singularly at ease. They sat, and while I answered cheerily,


fact a good thing, despite having initially completely misunderstood
they chatted of familiar things. But, ere long, I felt myself getting


it.
pale and wished them gone. My head ached, and I fancied a ringing


Hopefully this may be of use to anyone who lacks formal logic
in my ears: but still they sat and still chatted. The ringing


training, like [[jbocre: Jordan DeLong|myself]], in understanding exactly
became more distinct:--it continued and became more distinct:--


what mu'ei is all about.  (to those of you where leni do certu loi
I talked more freely to get rid of the feeling: but it continued and


logji cu zmadu tu'a mi, please correct any mistakes here, or feel
gained definitiveness--until, at length, I found that the noise was


free to expand stuff, etc.)
_not_ within my ears.


------
xorxes:


First let's say what a 'world' is, in the context of logic.  A world
lei pulji cu se mansa i le mi se tarti ba'o birtygau py i mi


is defined by the set of things which exist in that world, and the
mutce le ka surla i py zutse gi'e tavla fi loi slabu ca le nu


truth value of every proposition which can be made in the world.
mi gleki spuda i ku'i bazaku mi cinmo lo nu mi ca'o labybi'o


In modal logic, two new concepts are added to propositional logic
kei gi'e djica lo nu py ba'o cliva i mi cortu le stedu gi'e


which allow making claims across worlds, but it's really only one
se xanri lo nu lo se janbe cu nenri lei mi kerlo i ku'i py


concept since either can be written in terms of the other and
za'o zutse gi'e za'o tavla i le se janbe cu binxo lo satci


negation.  Specifically,
zmadu i ri renvi gi'e binxo lo satci zmadu i mi zifre zmadu


<nowiki>[] - necessary ([]p -> ~<>~p (not possible that not p))
tavla tezu'e lo nu cirko le se cinmo i ku'i ri renvi gi'e


<> - possible (<>p -> ~[]~p (not necessary that not p))
zenba le ka satci ibi'ibo bazaku mi facki le du'u le savru
</nowiki>


'Necessary' means that something must be true across all the worlds
ba'e na'e nenri lei mi kerlo


which can be 'accessed' from the current world, and 'possible' means
and:


it is true in at least one of those worlds. But what's it mean to
The police were satisfied. My conduct had been verified by them. I was


'access' worlds?
very much at my ease. As they sat talking about the same old stuff, I


Accessibility of a world from a different world is defined by a
happily replied, but as time went on, my emotion was one of blanching,


function R which takes the two worlds as arguments. The precise
and I wished for the police to be gone. My head ached, and I imagined


meaning of what it is for something to be 'necessary' or 'possible'
there to be ringing in my ears. But still the police sat and still they


is based on what R returns. For example, if we are dealing with
talked. The ringing grew more and more pronounced. I spoke more freely,


logical necessity, for a given pair of worlds w1 and w2, R(w1, w2)
so as to be rid of this feeling. But it persisted, getting ever more


returns true iff the logical rules of inference in both w1 and w2
clear, and I realized that the noise was in fact not inside my ears.


yield results consistent with the truth values in the world---in
xod:


other words you can only access worlds which conform to the rules
.i le pulji mo'u djica .i P co'a birti tu'a le mi seltarti .i mi kufra


of the logical system under which it is necessary. Different types
cai .i ca'o le za'i P zutse je casnu le slabu kei mi gleki spuda .i


of functions for R can be used to serve different purposes---allowing
ku'i mi ze'u cinmo le ka ce'u flira ciblu claxu gi'e djica le za'i P


discussion of different types of necessity (for example epistemological
cliva .i mi cortu le stedu gi'e ganse le lizyseljanbe goi L .i ku'i P


necessity or moral necessity); essentially any definition for R can
za'o zutse je casnu .i mi zenba L zu'e zi'o .i mi zenba le jei mi frili


give us a different modal system (and this appears to be how {mu'ei}
tavla kei zu'e mi tezu'e le pu'u rivbi L .i ku'i L stali .ibo mi zenba


lets us do a certain kind of [[jbocre: if|if]]).
L zu'e zi'o .i mi co'a jimpe le du'u mi ganse L sepi'onai le kerlo


The term 'possible worlds', then, refers to the set of worlds which
evgenis:


are accessible from the current world. I.e. the set of worlds w
The policeman has got what he wanted. He is almost convinced of


for which a true []p (in *this* world) makes a true p in w (and
my good behaviour. I feel very relaxed. As he keeps sitting and


note for pedantry that there's nothing to prevent that set from
chatting banalities I happily reply. Still, for a long while, I


including this world also, and many definitions of R (such as the
feel blood rushed from my face, and I want him to leave. My head


example logic-system based R) will be true for R(w, w) where w is
aches and I feel like buzzing. Still, he keeps sitting and


the current world).
talking. The buzzing feeling grows. I am earnestly trying to


The necessary and possible operators [] and <> are in this way
speak freely to get rid of him. Still, the feeling persists and


somewhat analogous to the universal and existential quantifiers of
grows. I start to understand that it is not with my ears that I


predicate logic (which, btw, makes it incidently nice that the
feel it.


mu'ei equivalents also involve ro and su'o).
pier:


romu'ei is the same as the [] operator and su'omu'ei means the <>
.i le pulji cu snada fi le nu djica


operator. This means that
.i ko'a jibni birti le du'u mi xamgu tarti


naku romu'eiku naku == su'omu'eiku
.i mi cinmo le ka tcesurla


naku su'omu'eiku naku == romu'eiku
.i ca'o lenu ko'a ca'o zutse tavla le fadni kei mi gleki spuda


Because mu'ei is in ROI and generalized to simply take a PA, we can
.iku'i mi ze'u ganse lenu le ciblu cu rinci le mi flira


make statements about things like so'emu'ei (I guess it's 'mostly
.ije mi djica lenu ko'a cliva


necessary'), though I don't think this feature is particularly
.i mi cortu le stedu gi'e ganse lo vrusli


compelling compared to giving us the [] and <> operators.
.i .oiro'i ko'a ca'o zutse je tavla


The portion of the mu'ei cmavo (the tagged sumti) which is intended
.i le vrusli selganse cu zenba


to allow rendering of [[jbocre: counterfactual correlation|counterfactual correlation]] essentially
.i mi junri zukte lenu flecu tavla lenu ko'a fesycliva


allows a way to specify some information about the R function:  what
.iku'i le selganse cu renvi gi'e zenba


is stated is that R(w, w') (where w is this world) will return true
.i mi co'a jimpe ledu'u mi ganse fi le mi na'e kerlo


if the proposition which is contained in the tagged sumti is a true
kreig:


one in w' (though it may be true or false anyway---it is just a
The police succeed because they want to. It nearly believes that I


hint to what R() means).
am a good behaver. I feel very relaxed. Continualy, the fact of its


----
continually sit-speaking to the ordinaries is happily replying to me.


May I dumb it down even further? A 'world' is a hypothetical or real situation. If you have world w1 and world w2 --- hypothetical situation A and hypothetical situation B --- one is accessible from the other if both of them 'make sense', and follow the same rules of logic.
But, for a long time, I sense that blood is draining from my face.


So if A has me blond and B has me a redhead, then A is accessible from B --- both make sense, neither ruptures the time-space continuum or whatever. But if A has me blond and B has me be my own father, then B is not accessible from A: it violates rules of logic which presumably hold in A.
And I want it to go away. I feel pain in the head and sense the


*The rules of logic are the same from world to world (for this purpose, anyhow), what is decisive here are certain facts in each world, including generalizations like "'father of' is irreflexive." pc
noise-oscillations. I am anxious; it continually sits and talks. What


If A is our real world, then B is any hypothetical situation that still follows the rules of logic. B can include you coming to work 10 minutes later than you did. It cannot include you killing your own grandfather before you were born. That scenario does not follow the rules of logic. You can tell, because it's a paradox. 'Possible world' really means just 'non-paradoxical scenario'.
the noise-oscillations sense is increasing. I act seriously, flowingly


*Yes, I think it is useful to view possible worlds as less than complete worlds (strictly, I suppose, sets of complete worlds which coincide in the scenario. Notice, though, that totally different worlds may be accessible from a world -- that is worlds with no overlapping scenario.  I take 'non-paradoxical' to mean 'not self-contradictory', but I am unsure whether -- for counterfactuals, e.g. -- we need to insist on that. pc
speaking to its wasteful departure. But that which is sensed survives


So in modal logic, we reason over the totality of hypothetical situations. If there's no way something could happen without violating the rules of logic, that's the same as saying there is no possible world in which it could happen. Any hypothetical scenario in which I kill my grandfather before I am born is not a possible world; it's an impossible world.
and increases. I, on being born, sense by means of my things which are


*relative to rules about procreation (and so to those worlds in which the meaning of 'grandfather' does not undergo major changes). Also I could, of course, kill the person in an alternate world who is my grandfather in this world without contradiction; modal logics make scope problems big time. pc
not really ears.


The reason 'worlds' are invoked is because hypothetical scenarios don't really otherwise fit into logic. Logic is all about propositions (''bridi'') about the world: they are either true or false. If you say "but it might have turned out different", propositional logic barks "whaddaya mean? It either happened or it didn't happen." Hypothetical scenarios have to be countable and orderable ''somewhere'', if a logic is to be able to deal with them. (And there isn't anything that logically outlandish about "but it might have turned out different", after all.) So modal logic calls these scenarios 'worlds', because it has to count them somehow. The ''possible world'' constraint is there so you don't use this as an excuse to say logically outlandish things. And it is, as it turns out, the standard logical way of dealing with the hypothetical.
noras:


Sorry to dumb it down yet further, Jordan, but I will likely write a textbook entry on this one of these days...
.i py. piso'amei birti jinvi le du'u mi xamgu tarti .i mi cinmo le ka


*Don't be sorry - I think I understood your explanation better than Jordan's. --pne.
mutce surla .i mi gleki spuda ca'o le nu py joi lei fadni cu zutse


-- [[User:Nick Nicholas|nitcion]]
casnu .ibazubo ku'i mi lifri le nu le ciblu cu rinci le flira .ije mi


Only silly stereotyping and deservedly maligned "common sense" differentiate the worlds that are possible from those impossible. We have no license to discuss worlds that conflict with our corpus of observations: we can discuss the possible world wherein Hillary is elected president in 2008, but not any where she was elected in 2000. --[[User:xod|xod]]
djica le nu py. cliva .i mi cortu le stedu gi'e ganse le savru nu


* Why not? Surely the pluperfect subjunctive (or some such thing) is a valuable as any other. For "what if" fiction, if nothing else. pc
desku .i mi xanka .ije ranji le nu zutse gi'e tavla .i mi ganse le nu


Natural language ''if'' is normally taken to involve not possible worlds in general, but rather, '''contextually relevant''' possible worlds. So, ''ro mu'ei'' should be understood as meaning "in all contextually relevant possible worlds". I think this covers Nick's point & xod's objection. Needless to say, some possible worlds are irrelevantly surreal in some contexts, but entirely pertinent in, say, sci-fi contexts. --[[User:And Rosta|And Rosta]]
le savru nu slilu cy zenba .i mi junri gasnu le nu flecu tavla le festi


----
nuncliva be le ciblu .iku'i le se ganse cu renvi gi'e zenba .i mi co'i


It seems to be that this whole notion depends upon making a distinction where none can be made. As if the outcome of a coin toss were actually exactly-50/50 (a computer can, given the initial forces, predict this outcome, however: it is itself a convention to assume they are equal)--whereas the outcome of a political election would be qualitatively different; & a world in which "[http://explorers.whyte.com/sf/bdf.htm ears discover fire]" more different still. What it comes down to, is a judgment upon the intellectually-separated subevent X, that it seems to have been either largely certain or largely contingent: & this is itself dependent upon your understanding (does the "butterfly effect" control your coin toss? depends on how much you've read, & how much you believe of what you've read--) of ''what CONTEXT means''. But for all this, i suppose it is useful to have a way of talking about these things ''bau la lojban.''. But i would prefer to have it arduous (using ''cei broda'') rather than simple: there are too many assumptions built into this usage, & Lojban does well to make us examine them. (''mi'e maikl.'')
le nu jbena cu ganse fi lo na'e kerlo


* All this stuff about possible worlds etc. is just an attempt to model the meaning of natural language conditionals, the sort of everyday logic that all people use quotidianly. I don't understand what you would prefer for us to say. I'd be interested to know, but it should maybe go under the [[jbocre: if|if]] page? --[[User:And Rosta|And Rosta]]
greg:


----
He almost certainly thought that I behaved well. I felt very relaxed. I


I'm not sure if this is the right place to pose this, but here it is anyway. From the point of view of surrealist literature how would one go about proposing an ''impossible'' world and comparing it to our current system?  Clearly you can't do this and have logic remain constant, but is there/could there be some method of signaling that logic might not hold for literary purposes?  In other words, how would you discuss the paradoxical situation where I kill my own grandfather? --[[User:skorgu|Skorgu]]
answered happily while he and the regulars sat talking. Some time


*You would discuss it the same way as in English. You can say, for example:
later, however, I felt the blood drain from my face and I wished he


''mi na ka'e zvati ti su'omu'ei le du'u mi pu catra le mi roryrorci pu le nu ri rorci le rorci be mi''
would leave. I had a headache and could feel loud shaking. I was


I couldn't be here had I killed my grandparent before he/she engendered my parent.
nervous and continued sitting and talking. I could feel the loud


*But you can also say:
vibration increasing. I make a serious attempt to talk fluidly to what


''mi pu ca'a catra le mi roryrorci pu le nu ri rorci le rorci be mi ije ku'i ue mi za'o zvati ti''
the blood had left behind, but the feeling stayed and increased. At


I did actually kill my grandparent before he/she engendered my parent, but (surprise!) I'm still here.
birth, I couldn't sense anything with my ears.


Thanks --[[User:skorgu|Skorgu]]
tsali:


* Note, as above, that this is not about logic, but about premises -- semantic axioms, say; what does "x is grandfather of y" entail. pc
le nanmu goi ko'a
 
ni'o ko'a jinvi ju'oru'e le du'u mi clite tarti
 
.i mi mutce surla
 
.i mi gleki spuda ca le nu ko'a joi le di'i vitke cu zutse je simtavla
 
.i ba za bo ku ku'i mi ganse le ka le ciblu cu rinci le mi flira .ije
 
mi pacna le du'u ko'a cliva
 
.i mi cortu fi le mi stedu gi'e ganse lo cladu ka desku
 
.i mi xanka gi'e ca'o zutse je tavla
 
.i mi ganse le ka le cladu ka desku cu zenba
 
.i mi junri troci le nu flecu tavla le se cliva be le ciblu .ije ku'i
 
le se ganse cu ranji gi'e zenba
 
.i ca le nu jbena mi na'e kakne cu ganse fi le mi kerlo
 
rab:
 
He indeed believed that I behaved politely. I relaxed greatly. I happily
 
responded when he and the regular guests sat and chatted. But later, I
 
felt the blood drain from my face, and I hoped that he would leave. I
 
got a headache and noticed a loud trembling. I was nervous, yet I still
 
sat and talked. I felt the trembling increase. I seriously tried to talk
 
flowingly to that which was left by the blood, but the feeling continued
 
and increased. My ear was stimulated during my inability to give birth.
 
--------------------
 
*[[User:xorxes|xorxes]]. ([email protected])
**English, Spanish, Esperanto
 
**French
 
*.[[jbocre: and|and]]. ([email protected].ac.uk)
**English
 
**Italian
 
*[[User:xod|xod]]. ([email protected])
**English
 
*[[jbocre: .evgenis.|.evgenis.]] ([email protected])
**English, Russian
 
**French, Italian, Esperanto
 
*[[jbocre: Pierre Abbat ier.|Pierre Abbat ier.]] ([email protected])
**English, French
 
**Other romance languages
 
*[[jbocre: .kreig.daniyl.|.kreig.daniyl.]] ([email protected])
**English, Spanish
 
*[[jbocre: Nora LeChevalier|Nora LeChevalier]] ([email protected])
** don't know, [[User:Bob LeChevalier|Bob LeChevalier]] didn't tell me.
 
*[[jbocre: .greg.|greg.]]daik. ([email protected])
**English, French, German(not quite but I ''can'' send and receive)
 
*[[User:tsali|tsali]] ([email protected])
**English, Norwegian
 
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*[[jbocre: rab.spir|rab.spir]]. ([email protected])
**English
 
**Spanish

Revision as of 17:12, 4 November 2013

Original (from "The Tell-Tale Heart" by Edgar Allan Poe):

The officers were satisfied. My _manner_ had convinced them. I

was singularly at ease. They sat, and while I answered cheerily,

they chatted of familiar things. But, ere long, I felt myself getting

pale and wished them gone. My head ached, and I fancied a ringing

in my ears: but still they sat and still chatted. The ringing

became more distinct:--it continued and became more distinct:--

I talked more freely to get rid of the feeling: but it continued and

gained definitiveness--until, at length, I found that the noise was

_not_ within my ears.

xorxes:

lei pulji cu se mansa i le mi se tarti ba'o birtygau py i mi

mutce le ka surla i py zutse gi'e tavla fi loi slabu ca le nu

mi gleki spuda i ku'i bazaku mi cinmo lo nu mi ca'o labybi'o

kei gi'e djica lo nu py ba'o cliva i mi cortu le stedu gi'e

se xanri lo nu lo se janbe cu nenri lei mi kerlo i ku'i py

za'o zutse gi'e za'o tavla i le se janbe cu binxo lo satci

zmadu i ri renvi gi'e binxo lo satci zmadu i mi zifre zmadu

tavla tezu'e lo nu cirko le se cinmo i ku'i ri renvi gi'e

zenba le ka satci ibi'ibo bazaku mi facki le du'u le savru

ba'e na'e nenri lei mi kerlo

and:

The police were satisfied. My conduct had been verified by them. I was

very much at my ease. As they sat talking about the same old stuff, I

happily replied, but as time went on, my emotion was one of blanching,

and I wished for the police to be gone. My head ached, and I imagined

there to be ringing in my ears. But still the police sat and still they

talked. The ringing grew more and more pronounced. I spoke more freely,

so as to be rid of this feeling. But it persisted, getting ever more

clear, and I realized that the noise was in fact not inside my ears.

xod:

.i le pulji mo'u djica .i P co'a birti tu'a le mi seltarti .i mi kufra

cai .i ca'o le za'i P zutse je casnu le slabu kei mi gleki spuda .i

ku'i mi ze'u cinmo le ka ce'u flira ciblu claxu gi'e djica le za'i P

cliva .i mi cortu le stedu gi'e ganse le lizyseljanbe goi L .i ku'i P

za'o zutse je casnu .i mi zenba L zu'e zi'o .i mi zenba le jei mi frili

tavla kei zu'e mi tezu'e le pu'u rivbi L .i ku'i L stali .ibo mi zenba

L zu'e zi'o .i mi co'a jimpe le du'u mi ganse L sepi'onai le kerlo

evgenis:

The policeman has got what he wanted. He is almost convinced of

my good behaviour. I feel very relaxed. As he keeps sitting and

chatting banalities I happily reply. Still, for a long while, I

feel blood rushed from my face, and I want him to leave. My head

aches and I feel like buzzing. Still, he keeps sitting and

talking. The buzzing feeling grows. I am earnestly trying to

speak freely to get rid of him. Still, the feeling persists and

grows. I start to understand that it is not with my ears that I

feel it.

pier:

.i le pulji cu snada fi le nu djica

.i ko'a jibni birti le du'u mi xamgu tarti

.i mi cinmo le ka tcesurla

.i ca'o lenu ko'a ca'o zutse tavla le fadni kei mi gleki spuda

.iku'i mi ze'u ganse lenu le ciblu cu rinci le mi flira

.ije mi djica lenu ko'a cliva

.i mi cortu le stedu gi'e ganse lo vrusli

.i .oiro'i ko'a ca'o zutse je tavla

.i le vrusli selganse cu zenba

.i mi junri zukte lenu flecu tavla lenu ko'a fesycliva

.iku'i le selganse cu renvi gi'e zenba

.i mi co'a jimpe ledu'u mi ganse fi le mi na'e kerlo

kreig:

The police succeed because they want to. It nearly believes that I

am a good behaver. I feel very relaxed. Continualy, the fact of its

continually sit-speaking to the ordinaries is happily replying to me.

But, for a long time, I sense that blood is draining from my face.

And I want it to go away. I feel pain in the head and sense the

noise-oscillations. I am anxious; it continually sits and talks. What

the noise-oscillations sense is increasing. I act seriously, flowingly

speaking to its wasteful departure. But that which is sensed survives

and increases. I, on being born, sense by means of my things which are

not really ears.

noras:

.i py. piso'amei birti jinvi le du'u mi xamgu tarti .i mi cinmo le ka

mutce surla .i mi gleki spuda ca'o le nu py joi lei fadni cu zutse

casnu .ibazubo ku'i mi lifri le nu le ciblu cu rinci le flira .ije mi

djica le nu py. cliva .i mi cortu le stedu gi'e ganse le savru nu

desku .i mi xanka .ije ranji le nu zutse gi'e tavla .i mi ganse le nu

le savru nu slilu cy zenba .i mi junri gasnu le nu flecu tavla le festi

nuncliva be le ciblu .iku'i le se ganse cu renvi gi'e zenba .i mi co'i

le nu jbena cu ganse fi lo na'e kerlo

greg:

He almost certainly thought that I behaved well. I felt very relaxed. I

answered happily while he and the regulars sat talking. Some time

later, however, I felt the blood drain from my face and I wished he

would leave. I had a headache and could feel loud shaking. I was

nervous and continued sitting and talking. I could feel the loud

vibration increasing. I make a serious attempt to talk fluidly to what

the blood had left behind, but the feeling stayed and increased. At

birth, I couldn't sense anything with my ears.

tsali:

le nanmu goi ko'a

ni'o ko'a jinvi ju'oru'e le du'u mi clite tarti

.i mi mutce surla

.i mi gleki spuda ca le nu ko'a joi le di'i vitke cu zutse je simtavla

.i ba za bo ku ku'i mi ganse le ka le ciblu cu rinci le mi flira .ije

mi pacna le du'u ko'a cliva

.i mi cortu fi le mi stedu gi'e ganse lo cladu ka desku

.i mi xanka gi'e ca'o zutse je tavla

.i mi ganse le ka le cladu ka desku cu zenba

.i mi junri troci le nu flecu tavla le se cliva be le ciblu .ije ku'i

le se ganse cu ranji gi'e zenba

.i ca le nu jbena mi na'e kakne cu ganse fi le mi kerlo

rab:

He indeed believed that I behaved politely. I relaxed greatly. I happily

responded when he and the regular guests sat and chatted. But later, I

felt the blood drain from my face, and I hoped that he would leave. I

got a headache and noticed a loud trembling. I was nervous, yet I still

sat and talked. I felt the trembling increase. I seriously tried to talk

flowingly to that which was left by the blood, but the feeling continued

and increased. My ear was stimulated during my inability to give birth.


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