Core Thesis
Proper names and natural kind terms are rigid designators that refer to the same object across all possible worlds—not via descriptive content, but through causal-historical chains of reference. This ruptures the traditional identification of necessary truth with the a priori, revealing an entire class of necessary a posteriori truths.
Key Themes
- Rigid Designation: Names lock onto their referents in every possible world, regardless of contingent properties
- The Causal Theory of Reference: Reference transmits through a causal chain from an initial "baptism" event, not through associated descriptions
- Necessary A Posteriori: Some truths (e.g., "Water is H₂O") are metaphysically necessary yet empirically discovered
- Contingent A Priori: Some truths (e.g., "The standard meter is one meter long") are known independently of experience yet contingent
- Scientific Essentialism: Natural kind terms pick out essences discoverable only through empirical investigation
- Critique of Descriptivism: The Frege-Russell view that names are shorthand for definite descriptions is fundamentally mistaken
Skeleton of Thought
Kripke begins by dismantling the dominant Frege-Russell orthodoxy: the view that a proper name refers by virtue of some associated description (e.g., "Aristotle" = "the teacher of Alexander the Great"). He demonstrates that this view fails on three distinct grounds—epistemic, semantic, and modal. We can successfully refer without knowing uniquely identifying descriptions; descriptions fail to pick out the right object in all cases; and critically, names behave differently from descriptions in modal contexts. If "Aristotle" meant "the teacher of Alexander," then "Aristotle might not have taught Alexander" would be self-contradictory. But it isn't—it's a perfectly coherent modal claim. Names are thus rigid: they designate the same object in every possible world where that object exists.
This leads Kripke to his central technical innovation: the distinction between rigid and non-rigid designation. A rigid designator picks out the same entity across all possible worlds; a non-rigid designator (like "the president of the United States") picks out different entities in different worlds. This is not merely a technical point but a deep insight into how language hooks onto reality. The mechanism, Kripke argues, is causal: a name is introduced in an initial "baptism"—perhaps by description, perhaps by ostension—and then passes from speaker to speaker along a communicative chain. Later speakers need not know any identifying descriptions; they need only intend to refer to whatever their source referred to.
The explosive consequence follows: if "Hesperus" and "Phosphorus" are both rigid designators for Venus, then "Hesperus is Phosphorus" is necessarily true—true in all possible worlds. Yet this identity was discovered empirically, through astronomical observation. Hence: a necessary truth known a posteriori. The same logic applies to scientific identities like "Water is H₂O" or "Heat is molecular motion." Kripke thus severs the Kantian conflation of the necessary/contingent distinction with the a priori/a posteriori distinction. These are two independent axes, generating a four-part classification rather than a simple dichotomy. This revival of a robust modal metaphysics—of essences and necessities discoverable only through science—represents a decisive break with the logical positivist tradition.
Notable Arguments & Insights
The Gödel Case: If "Gödel" meant "the discoverer of the incompleteness theorem," and it turned out Schmidt actually discovered it, "Gödel" would refer to Schmidt—but intuitively, we're still talking about Gödel, the man we learned about under that name. Reference is not determined by description.
The Modal Argument: "The number of planets might have been different" is true. But "Nine might not have been nine" is false. So "the number of planets" and "nine" function differently—one is non-rigid, the other rigid.
Scientific Essentialism: Before chemistry, "water" was a term for whatever substance filled lakes and rivers. But once we discovered that water is essentially H₂O, we learned something necessary about water—not a linguistic convention but a metaphysical fact about its essence.
The Standard Meter: "The standard meter stick is one meter long" is knowable a priori (we fixed the reference by that very stick) yet contingent (the stick could have been different). This is the mirror image of the necessary a posteriori.
Against Type-Type Identity Theories: If pain = C-fiber firing is a contingent identity, then in some possible world, pain exists without C-fiber firing. But if "pain" and "C-fiber firing" are rigid designators, this identity would be necessary. This argument reshaped philosophy of mind.
Cultural Impact
Naming and Necessity is widely regarded as the most influential work in analytic philosophy since World War II. It single-handedly revived metaphysics from the parsimonious restrictions of logical positivism, making modal notions respectable again. The work catalyzed the development of direct reference theory, transformed philosophy of mind (via arguments against psychophysical identity theories), and established the foundations for contemporary debates about natural kinds, scientific realism, and essentialism. Kripke's casual lecture style—preserved in the transcript format—became iconic: philosophy as urgent, improvisational, ferociously intelligent conversation.
Connections to Other Works
- "On Sense and Reference" by Gottlob Frege — The classic statement of the descriptivist view Kripke dismantles
- "On Denoting" by Bertrand Russell — Russell's theory of definite descriptions, extended by Kripke to proper names
- "The Meaning of 'Meaning'" by Hilary Putnam — Extends Kripke's externalism to natural kind terms; the Twin Earth thought experiment
- "Frege's Puzzle" by Nathan Salmon — Contemporary development of Kripkean themes in philosophy of language
- "Philosophical Investigations" by Ludwig Wittgenstein — Kripke's later work on rule-following engages deeply with Wittgenstein, forming a separate but related legacy
One-Line Essence
Names latch onto the world through causal chains, not descriptions—and in so doing, they reveal that some truths are both necessary and discovered.