“When I use a word,” Humpty Dumpty said in rather a scornful tone, “it means just what I choose it to mean—neither more nor less.”

I’m sure many people have had this idea before me, but now that I’ve had it, let me commit it to paper as a means of helping myself think it through.

A language is a contract. It’s a contract negotiated between many parties (its speakers) and its clauses are things like, “when I say peach I mean [that fuzzy fleshy fruit], you know what I mean” and you can trust that they know what you mean because it’s all in the contract. There are millions if not billions of these clauses—not just for words but also for phrases and idioms and gestures and speech-acts.

You hold up your end of the bargain because you recognise that if everybody holds up her own end of the bargain, then you all have the power to communicate with each other. You can say peach to Krishna and be assured that the neurons for [that fuzzy fleshy fruit] are activated in her mind because she is bound to the same contract, the one with clauses that say peach means [that fuzzy fleshy fruit].

If either of you do not uphold the contract, then you mutually lose the ability to communicate with each other. If you want to convey [scaly octopus appendage] to Krishna but you say peach, then she will not think [scaly octopus appendage] but rather [that fuzzy fleshy fruit], and the communication will be a failure. On the other hand, if you want to convey [that fuzzy fleshy fruit] to her by saying peach but she doesn’t uphold the contract, then she won’t receive [that fuzzy fleshy fruit] and the communication will also be a failure.

One reason Krishna may fail to uphold her end of the contract is that she may in fact be adhering to an entirely different contract! Perhaps she has entered an agreement where the word for [that fuzzy fleshy fruit] is pesca and the word for [scaly octopus appendage] is tentacolo. That is entirely her prerogative. In this specific case, she is a signatory to a contract called “Italian” and you, to a contract called “English”. One of you will have to uphold the other’s contract, that is, learn the other’s language, in order to gain the power of communication.

That much is obvious. It’s what language is, and it’s what a contract is. Languages are contracts. Two corollaries, vaguely in opposition:

Contracts can be re-negotiated. Suppose gay means [happy] but you want it to mean [homosexual] instead. You can convene a quorum of contract signatories and get everyone to agree that when you say gay you want to activate the neurons in their brains that correspond to [homosexual]. Realistically, this doesn’t happen all at once, but instead over a matter of years or decades. And it doesn’t begin with everybody in on the change, but it starts with small groups of language-influencers and ripples out into the larger crowd. And many such renegotiations are happening constantly and in parallel. This is how a language evolves.

English traditionalists like to lament that English is getting worse and worse with each passing generation. But in this metaphor, language change is not bad, any more than a renegotiation of contracts is a bad thing. It’s not necessarily a good thing, either. It’s neutral. There will be some who like the snapshot of what the contract was like in 1972, and others who are dreaming up what the contract might look like in 2072. Neither party is necessarily better than the other.

You can’t change a contract unilaterally. Suppose gay means [happy] but you want it to mean [homosexual]. You can use the word gay and hope you’re activating the neurons for [homosexual] in Krishna’s brain, but because gay actually means [happy], you’ll actually end up activating the neurons for [happy] instead. Even though you might wish that gay meant [homosexual] instead, you can’t unilaterally wish that change into existence, any more than you could wish peach to mean [scaly octopus appendage]. It has to go through the re-negotiation process first.

This is why Humpty Dumpty’s proclamation, A word means what I say it means, rings so false. Humpty Dumpty is trying to unilaterally change the contract by sheer assertion. That’s not how contracts work.