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On 6/16/14 2:05 AM, John F Sowa wrote:
Pat,
That is an important question:
> But its not at all obvious what a proposition *is*. For sure, it can't
> be simply a sentence or even an equivalence class of sentences. It
> can't be anything that is defined purely in terms of syntax, because
> propositions, unlike sentences, are typically *about* something.
> Consider for example, the proposition that I, Pat Hayes, am an
> American citizen. You can write a sentence
>
> (American PHayes)
>
> but what ensures that the name "PHayes" refers to me?
And as usual, Peirce anticipated that question and answered it.
He coined the term 'indexical' and said that every proposition must
contain at least one indexical (pointer, such as a gesture, physical
link, or convention) that ties its symbols to the intended referent.
He said that proper names, such as 'PHayes', are symbols whose
conventional meaning is to serve as indexicals of their referents.
The method of following that pointer to its intended referent
depends on the conventions of the culture and available technology.
He didn't anticipate the WWW.
As an example, he said that a portrait hanging on the wall is
an icon, and it does not state a proposition. But a name in the
corner of a portrait, by convention, asserts the proposition
that the named person was the artist. A name on the frame beneath
the portrait, by convention, asserts the proposition that the
portrait is an icon of the named individual.
John,
Changing the subject line to bring focus to yet another important
area that's sometimes a source of confusion.
Peirce might not have anticipated the World Wide Web, but the World
Wide Web is all about exploiting the use of 'indexicals' as he
perceived them.
Example:
Every HTTP URI denotes an Entity.
Every HTTP URI resolves to a Description of its Referent.
To make the Description of what a URI denotes comprehensible to both
Humans and Machines, via Web Documents, we have RDF based Linked
Data.
RDF, by being based on IRIs (rather than HTTP URIs solely)
introduced a deep flexibility that's also lost in confusion. For
instance, there might be times when a local identifier suffices
e.g., industry standard or national codes.
Links:
[1] http://bit.ly/WAJGCp -- Linked Data explained in a single slide
[2] http://bit.ly/10Y9FL1 -- World Wide Web proposal tweaked to
reflect use of indexicals via HTTP URIs
[3] http://bit.ly/UFvdKV -- Simple Linked Data Tutorial based on
HTTP URIs with fragment identifiers (showcasing indexicals without
invoking explicit content negotiation).
--
Regards,
Kingsley Idehen
Founder & CEO
OpenLink Software
Company Web: http://www.openlinksw.com
Personal Weblog: http://www.openlinksw.com/blog/~kidehen
Twitter Profile: https://twitter.com/kidehen
Google+ Profile: https://plus.google.com/+KingsleyIdehen/about
LinkedIn Profile: http://www.linkedin.com/in/kidehen
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