I want to consider how the relatively common (and not particularly controversial) practice of stipulatively introducing terms into a language fares relative to three conceptions of the basic business of semantic theories. The three conceptions I am interested in are:
A) Propositional semantics
B) Expressivist semantics
C) Speech-act Theoretic Semantics
Very roughly, the (A) conception of semantics is one on which the business of semantics is to assign propositions to sentences. On this type of view, a basic idea is that a true utterance of some sentence will place constraints on how the world can be, and the job of a semantic theory is to assign a proposition that is properly related to those constraints.
Very roughly, the (B) conception of semantics is one on which the business of semantics is to assign mental states to sentences. On this type of view, a basic idea is that the sincere utterance of some sentence will require certain goings-on in the speaker's mind, and the job of a semantic theory is to assign a mental-state that is properly related to those requirements.
Very roughly, the (C) conception of semantics is one on which the business of semantics is to assign speech-acts to sentences. On this type of view, a basic idea is that a successful utterance of some sentence will have certain effects on the conversation or audience, and the job of a semantic theory is to assign a speech-act that is properly related to those effects.
I've obviously oversimplified these views a great deal, and we could quibble about my formulations or about what I take to be key components of the views, but, this rough sketch of the views is sufficient for my purposes.
Now, if the only mental state ever proponents of (B) invoked was belief, and the only speech-act proponents of (C) ever mentioned was assertion, and the thing one needed to believe for sincerity always lined up with the assertion made by successfully uttering it, and that thing also lined up with what the world needed to be like for the sentence to be true, it would not seem like these conceptions were really at odds with one another. However, proponents of (B) do not assign _only_ beliefs to sentences, and proponents of (C) do not assign _only_ assertion. Theorists who find (B) appealing may be motivated by non-cognitivism about normative terms, or by the desire to offer a semantic treatment of slurs or pejoratives (either of which could involve assigning non-cognitive mental states to sentences containing the respective terms). Proponents of (C) might be motivated by wanting to distinguish conditional assertion from the assertion of a conditional. These clearly aren't all the reasons one could be pulled towards the views, but just a way to see how the (B) and (C) conceptions can genuinely come apart from (A) and from each other.
My interest in this post is in how these conceptions of semantics interact with the practice of introducing a new term and giving it a stipulated definition. Here is a brief example of the practice:
Let 'garzy' be a common noun that picks out all parties having at least 100 attendees and only parties having at least 100 attendees.
Now that we've introduced 'garzy', I can use it: If I were the sort of person inclined to do such things, I could go around talking about garzies, ask people whether the gathering they attended was a garzy, and I could attempt to plan a garzy, etc. Some of these require people to go along with my introduction and use the term themselves, but that doesn't cause problems for my investigation.
I want to contrast the foregoing example with the following pair of cases:
1. Let 'morko' be a common noun that picks out all people who read philosophy blog posts, and only people who read philosophy blog posts, and, further, let it be the case that sentences using 'morko' express the attitude of hatred towards people who read philosophy blog posts.
Now that I have introduced 'morko', it seems like I can use it, but not quite as I have stipulated. For instance, I can say that, spammers aside, only morkos comment on my blog posts, and I can ask whether morkos are making up an increasing proportion of blog readers in general, etc. Now I'm not 100% sure that those previous sentences were meaningful/good in the relevant sense, but I am sure that I didn't just express hatred for people who read philosophy blog posts, and that the sentences I used don't express hatred for people who read philosophy blog posts.
2. Let 'rutu' be a common noun that picks out all bananas and only bananas, and further, let it be the case that sentences using 'rutu' express (in addition to the assertoric speech-acts they would ordinarily have, the speech act of apologizing for discussing bananas.
Now that I have introduced 'rutu', it seems like I can use it, but not quite as I have stipulated. For instance, I can say that my favorite fruit is the rutu (though the assertion would be false), and I can ask whether you had any rutu in the last week or so, etc. However, I don't think I've apologized for discussing bananas, and I don't think the sentences I used express an apology for discussing bananas.
Now, it isn't all-by-itself a problem for the (B) or (C) conceptions that I can stipulate truth-conditional contributions of an invented term and start using it pretty easily. And it isn't all-by-itself a problem for the (B) or (C) conceptions that I can't stipulate any expressivist or speech-act theoretic contributions of an invented term and start using it pretty easily. However, those two things combined do seem to raise a question for those conceptions of semantics: Why is it that some parts of semantics can be stipulated and not others? The (A) conception is the only one on which invented terms can have their semantic values given straightforwardly by stipulation. The (B) conception allows new terms to have a stipulative contribution to what belief might be required for sincere utterance of the sentence, but not for non-cognitive contributions to the semantic value. The (C) conception allows new terms to have a stipulative contribution to what assertion is made by successful utterance, but not for non-assertoric contributions to the semantic value. There may be some explanation for why only the semantic values that map neatly onto (A)-type conceptions of semantic value can be stipulatively defined, but it seems like one is needed. I should also note that I'm not basing the argument on some pre-theoretic intuition that semantic value should be apt for stipulative definition, rather, I am noting a contrast within the realm of (B)- and (C)-type semantic values, and observing that there should be some account of why there is such a contrast.
I should note that not everyone seems to agree with me on the inability to stipulate these other sorts of contribution. Dave Barnett, for instance, in a paper on conditionals, stipulatively introduces a connective that has a suppositional semantics, and, if I remember correctly, in "Thinking How to Live", Alan Gibbard introduces a stipulatively expressive predicate in one chapter (I'll have to verify both of these. At least one of them may have been a thought experiment about what would happen if some possible term had such-and-such semantics, which is quite different from the stipulative definition of an actual term as having those semantics).