: That in order to have a coherent thought, you must know what you are thinking about; in particular, you must have some kind of distinguishing knowledge of the referents of singular terms in your thought--i.e. a way of distinguishing them from other things.
Suppose you receive a postcard that says simply, 'I wish you were here,' with no pictorial representation of where 'here' is. Suppose, for this first case, that it's signed, so the only unknown is where 'here' is. Do you understand the sentence? My inclination is to say, yes and no. You understand it as a sentence containing a variable standing for 'the place where I [the writer] am,' wherever that happens to be. And the way you understand a sentence like that is certainly different from the way you understand a sentence with no undetermined referents. Why? Because you will invariably puzzle over where 'here' is. You have received a little mystery. You do, however, understand the kind of thing 'here' stands for: some place or other, where the writer is located at the time of writing.
John Perry's response is--extremely roughly--that you think of the referent of 'here' casually; this doesn't seem quite right to me. And that since you can, with the right resources, figure out what it is, then you know what its referent is. I agree that you can sometimes figure it out. And if there were no causality, and no event was connected to any other, this--and much else--would be rather difficult. But I think you can figure it out because you know that 'here' refers to the place the writer was at the time of writing. (For all I know, this is Perry's current position. I haven't read Reference and Reflexivity
yet. But he does love to talk about ambiguous postcards as counterexamples to Russell's Principle.)
This effect is magnified if the sentence you're presented with contains more than one indexical or demonstrative with an unknown referent. On the wall above, 'It's you I love' is undetermined for both 'you' and 'I.' Supposing it actually was written by one person for another, we understand it to be one person telling another that they love them. And that is about all one understands. It's an empty schema. You can only imagine the circumstances that occasioned it.
It's also possible that it was written as an empty schema
, in order to puzzle people, or to symbolize the act of telling someone that you love them; in this case there is no referent. It's art. This case is perhaps the furthest from any possibility of an ordinary understanding of the sentence. Not only is it an empty schema: it was written in order to be one. It's a representation of a type of utterance. It's not an utterance at all. (This case is interesting, because these sorts of thing are everywhere these days: mottos inscribed on things. They're not actual utterances--no one is saying them. And it's not clear who no one is saying them to
. Yet we surround ourselves with them.)
All of this puts aside the more complex problem that even a sentence like 'wish you were here' might not have the meaning it superficially appears to have. It might be sarcastic: "Vesuvius in eruption. Wish you were here." There might be still more to the context of a spoken or written utterance than simply the referents of indexicals and demonstratives that we need to know in order to understand the utterance. If I turn on the television and see one character say to another, "It's you I love," having not seen what preceded that, though I will know its referents (sort of: this person and that person--though I may be intrigued to watch more to find out which particular people they are in the show's universe)--and I may be able to determine from its tone whether it's sincere, I won't really know its import, having not seen what preceded it. If I open a book I've never read to a random page and see "It's you I love" written there, then, though I may be able to see that it occurs in a conversation and thus is not a piece of conceptual art, I will be able to determine just from reading that sentence neither its sincerity, nor its import, nor the referents of 'you' and 'I.' I will, however, know the sorts of things 'you' and 'I' stand for--so long as they occur in ordinary speech. They stand for people (or, in this case, fictional people). I will have to read the rest of the story, however, to find out who.
I would like, then, to partially uphold Russell's Principle. I think the way one understands a sentence with indexicals and demonstratives whose referents one doesn't know is quite different from the way one understands a sentence with indexicals and demonstratives whose referents one does know. And I think that this ability to come to know said referents rests primarily on understanding the way such terms work--the sorts of things they refer to.