Imagine walking into a lecture hall in 1970 and watching a young man with a messy beard dismantle 200 years of logic in three days. That was Saul Kripke. He didn't have notes. He just talked. The result was Saul Kripke Naming and Necessity, a book that basically flipped the table on how we think about language, identity, and the very fabric of what is "possible."
Before Kripke, everyone thought they had it figured out. If you said "Hesperus is the evening star," you were just describing a thing by its properties. Kripke said, "No, that's not how names work at all."
He introduced us to the "Rigid Designator." It sounds like a sci-fi gadget, but it's actually the reason you are still you in every possible universe.
The Descriptive Trap: What Frege and Russell Got Wrong
For a long time, the heavy hitters like Gottlob Frege and Bertrand Russell argued that names are just shorthand for descriptions. Think about Aristotle. To Russell, "Aristotle" just meant "the teacher of Alexander the Great" or "the author of the Nicomachean Ethics."
It makes sense on the surface. But Kripke noticed a massive flaw.
If "Aristotle" meant "the teacher of Alexander," then the sentence "Aristotle taught Alexander" would be a tautology. It would be like saying "the bachelor is unmarried." It would be impossible for Aristotle to have skipped that teaching gig and gone into carpentry instead.
But we know he could have.
Kripke argues that names don't have "senses" or "meanings" in that way. They are pointers. He calls them rigid designators. A rigid designator picks out the same object in every single possible world where that object exists.
Possible Worlds and the Modal Revolution
When we talk about "possible worlds," we aren't talking about Multiverse movies or Doctor Strange. We're talking about counterfactuals. Basically, ways the world could have been.
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In some world, you ate a bagel this morning instead of toast. In another, the Roman Empire never fell.
Kripke's big move in Saul Kripke Naming and Necessity was separating "necessity" from "analyticity." Before him, philosophers thought that if something was necessarily true (it couldn't be any other way), you had to be able to figure it out just by looking at the words.
Kripke proved that's not true.
Take the statement "Water is $H_2O$."
Is it necessarily true? Yes. In any world where you have that specific substance, it's made of those molecules. If it were $XYZ$, it wouldn't be water; it would be something else that looks like it. But is it "a priori"? Can you know it just by thinking? No. You need a lab. You need science.
This gave us the Necessary A Posteriori. It was a total brain-breaker for the 1970s academic scene.
The Baptism and the Causal Chain
So, if names aren't descriptions, how do they work? How do I know who "Richard Nixon" is if I wasn't there to see him?
Kripke suggests a "causal theory of reference."
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- An object is "baptized" (given a name).
- That name is passed from person to person.
- The chain continues down to you.
You don't need to know a single fact about the guy to refer to him. You just need to be part of the chain. You're "borrowing" the reference from the person you heard it from. Honestly, it's a lot more like how we actually use language than the weird, complex descriptive clusters the old guard suggested.
The Identity Crisis: Hesperus and Phosphorus
People used to think Hesperus (the evening star) and Phosphorus (the morning star) were two different things. Then, astronomers realized they were both just Venus.
Old-school logic said that "Hesperus is Phosphorus" is a contingent truth—something that just happened to be true but could have been different.
Kripke says: Wrong. If Hesperus is a rigid designator for Venus, and Phosphorus is a rigid designator for Venus, then they are the same thing in every world where that planet exists. The identity is necessary. We just discovered it empirically.
This leads to some wild conclusions about the mind and body.
Why This Scares Materialists
If you say "Pain is the firing of C-fibers," and both "Pain" and "C-fiber firing" are rigid designators, then that identity must be necessary. It would have to be true in every possible world.
But Kripke points out that we can easily imagine a world where C-fibers fire but there is no feeling of pain. Or a world where there is pain but no C-fibers.
Since we can conceive of them being separate, they aren't necessarily the same. And if they aren't necessarily the same, then—according to the rules of rigid designation—they aren't the same at all.
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This "Modal Argument" is still one of the biggest headaches for neuroscientists and philosophers trying to prove that the mind is just the brain.
Why Naming and Necessity Still Matters in 2026
You might wonder why we’re still talking about a series of lectures from over fifty years ago.
It’s because Kripke changed how we handle "essences." He brought back the idea that things have an actual nature. A cat isn't just a "small furry thing that meows." A cat is a biological entity with a specific DNA structure. Even if it didn't meow and had no fur, it would still be a cat if it had that essence.
This affects how we categorize everything from species to chemical elements.
It also keeps us honest about our limitations. We realize that there are truths about the world that are baked into the logic of reality, but we can't find them just by sitting in an armchair and thinking hard. We have to go out and look.
Actionable Takeaways for the Curious Mind
If you want to apply Kripkean logic to your own thinking, start with these steps:
- Question your definitions. Stop assuming that a name is just a list of traits. When you talk about a person, you are talking about them, not their resume or their personality. This changes how you view identity and loyalty.
- Differentiate between "could have been" and "must be." Practice identifying which facts about your life are contingent (like where you live) and which are essential (like your origins).
- Watch for the "Descriptive Fallacy" in arguments. People often try to win debates by redefining words. If you hold to the idea of rigid designation, you can see through these linguistic tricks more easily.
- Read the source. Naming and Necessity is surprisingly readable. It’s a transcript of a talk, not a dry textbook. Pick up the Harvard University Press edition. It’s short, punchy, and will make you feel like your brain is getting a much-needed stretch.
The world isn't just a collection of descriptions we’ve slapped onto a blank canvas. It’s a place of real things with real identities that persist across every "what if" we can imagine.