We often say what we want to say in fewer words than might seem possible.
Do you see the table over there? Yes. Do you see the red block on it? Yes. Good. Please bring it to me.
That first it saves the speaker from having to say that table again. The second it does the same for the red block. Accordingly, many people consider a pronoun like it to be an abbreviation or substitute for another phrase used recently. But when we look at this more carefully, we see that a pronoun need not refer to any phrase at all. For instance, the word this in the previous sentence was not an abbreviation for any particular phrase. Instead, it served as a signal to you, the reader, to examine more carefully a certain partial state of mind — in this case, a certain theory about pronouns — that I assumed was aroused in your mind by the sentences that preceded it. In other words, pronouns do not signify objects or words; instead, they represent conceptions, ideas, or activities that the speaker assumes are going on inside the listener's mind. But how can the listener tell which one of the activities is signified when there are several possibilities?
Do you remember the ring Jane liked? Yes. Good. Please buy it and give it to her.
How do we know that her means Jane and that it means the ring — and not the other way around? We can tell that her is not the ring because English grammar usually restricts the pronoun her to apply only to a female person — though it could also mean an animal, a country, or a ship. But you would know that it means the ring in any case, because your Buy agency would not accept the thought of buying Jane, nor would your agency for Give accept the thought of giving gifts to rings. If someone said, Buy Jane and give her to that ring, both Buy and Give would have such strong conflicts that the problem would ascend to the listener's higher-level agencies, which would react with disbelief.
Our language often uses pronounlike words to refer to mental activities — but we do not do this only in language: it happens in all the other higher-level functions of our minds. Later we'll see how Find will find a block — rather than, say, a toy giraffe — even though Builder has only said find. The trick is that Find will use whichever description happens to be available in its current context. Since it's already working for Builder, its subagents will assume that it should find a building-block.
Whenever we talk or think, we use pronounlike devices to exploit whatever mental activities have already been aroused, to interlink the thoughts already active in the mind. To do this, though, we need to have machinery we can use as temporary handles for taking hold of, and moving around, those active fragments of mental states. To emphasize the analogy with the pronouns of our languages, I'll call such handles pronomes. The next few sections speculate about how pronomes work.