I've heard of a few different stipulative definitions for the term "proposition", but being a stipulative definition isn't a sufficient condition of being a technical definition. I think given some time, I could come up with a good stipulative definition for the term, but it'll reflect my views on what it means, yet the slightest difference between my stipulative definition and the technical definition commonly used by fluent users of the technical term will render my use as incorrect if I try to pawn it off as how it's ordinarily used by fluent speakers of that technical term.
There is NO single definition used by philosophers (= fluent users of the technical term). Quoting SEP in the before linked article. There is no single meaning that you are looking for. There is also a lot of somewhat related meanings of the technical usage of "proposition". That may be unsatisfying but it is the truth.
The term 'proposition' has a broad use in contemporary philosophy. It is used to refer to some or all of the following: the primary bearers of truth-value, the objects of belief and other "propositional attitudes" (i.e., what is believed, doubted, etc.), the referents of that-clauses, and the meanings of sentences.
Although I'll sometimes cite that definition, I do actually have a number of problems with it. First and foremost, I would absolutely scrap the use of the word "what." I think it's terribly uninformative.
Maybe it is terribly uninformative and you can try with odd analogies if you wish, but the fact remains that without propositions it is terribly hard to deal with certain problems, especially related to truth carriers. Hence why many if not most philosophers simply bite the sour apple (so to speak) and accept propositions. Quoting Swartz (not "Schwartz" as Ken very often writes!):
Although I generally prefer negative theories - those which posit as few unempirical concepts* as possible - my own leanings in this
23 particular case are toward Realism. My attraction to the theory is bolstered by one further consideration: I can see no way to account for the existence of certain items, e.g. pieces of music, plays, and novels, other than by conceiving of them as abstract entities. Here I am considerably inﬂuenced by the arguments of C.E.M. Joad (1891-1953).
Joad argued (, 267-70) that the play Hamlet, for example, could not reasonably be identiﬁed with any particular in the world: neither 24 with an idea in Shakespeare 's mind, nor with any manuscript he wrote, nor with any printed edition of the text, nor with any particular production, nor with any audio or video recording of any particular production. F r Hamlet could exist even if any one or several of these were not to exist. While Joad, himself, rightly expressed some difﬁdence about his own arguments, I think that they add considerable impetus to a theory which would posit abstract entities.
Although I am a Realist, I am a reluctant Realist. F r, to be frank, there is something exceedingly peculiar about positing entities which exist (subsist) outside of space and time. I, personally, would prefer a theory which could dispense with such mysterious entities. But I ﬁnd the problems inherent in the various anti-Realist theories even more troubling. Realism is simply the better, in my estimation, of the available theories. But, like many other Realists, I do not much care for Realism. Recently one of my colleagues professed his repudiation of Realism by saying that he found the positing of abstract entities " unintelligible ". I share his displeasure. But I ﬁnd myself unable to adopt his own anti-Realist position because I cannot in turn believe that the anti-Realist theories provide any better answer or that they can be developed without themselves having to posit at least some abstract entities.
Norman Swartz, Beyond Experience
, pp. 270-272, available online
Secondly, when I say that a proposition is ..., I will be using the is of identity. Third, I'd work on the other problems one of which is the fact not all declarative sentences express propositions.
As for not all declarative sentences expressing propositions, that depends on what "sentence" means. Some definitions of "sentence" implies meaningfulness. If so, one has to ask: Do all meaningful declarative sentences express propositions? I am inclined to think that the answer is "yes". At least, I cannot this moment think of a counter-example.
Another problem is the fact that some sentences that are not declarative sentences can actually express a proposition.
This I agree with but I think that it is an uncommon view. At least, I've never seen anyone else say this.
I think the fact propositions are true or false needs to be informatively incorporated into the definition. In addition, a much better grip needs to have been gotten on just what the heck "what" refers to.
Actually that would be a very bad idea since it would beg the question against gap-theories and maybe dialetheists too depending on the precise formulation. The definition needs to not beg the question, that should be obvious.
Furthermore, there's something else going on that I can't quite put my finger on. There's an air of implied dependency, as if the sentence is somehow a requirement for the existence of propositions (this issue hasn't been settled, as far as I know). In analogy, yes, Jupiter is something that is viewed through a telescope (just as a proposition is something expressed by a sentence), but what Jupiter is is independent of telescopes, but it's not at all clear (given how the definition is worded) whether or not sentences are a necessary condition for propositions.
Maybe not, but I'd say that almost all persons that accept propositions think they are abstract objects. That answers your question about dependencies. Abstract objects exist necessarily.
Abstract? I can see why you'd say they are without location (so possibly quasi abstract), but why do you think they are non-temporal (and thus abstract)?
It is a technical term. See SEP
Abstract Objects (Stanford Encyclopedia of Philosophy)
Try to frame a theory with truth carriers as temporal and you will find many problems. Most of the problems I know are nicely solved by truth carriers being non-temporal. Though it is not that uncommon to believe that truth carriers are temporal cf. the tomorrow's sea battle (a famous problem) about future contingent truth carriers.
Some other problems with temporal truth carriers are mentioned here
and in the book referred to at the bottom.
I used the analogy before about how I would hate for someone to define "baseball" as something hit by a baseball bat; moreover, I would hate for someone to define "proposition" as something expressed by a sentence, since "something" (much like "what") isn't very helpful. Of course, it's not defined as something expressed by a sentence but instead what is expressed by a sentence (I'm just using the short version definition for brevity), but both are equally (and poorly) informative.
I dislike analogies. I'll just ignore this one.
---------- Post added 06-02-2010 at 01:20 AM ----------
A proposition is a truth-bearer; it describes a truth or falsity about the world. I'm assuming this won't suffice, but there it is.
This begs the question against gap-theories. See my post above to Fast as he proposed a definition with the same problem.