A causal theory of reference is a theory of how terms acquire specific referents based on evidence. Such theories have been used to describe many referring terms, particularly logical terms, proper names, and natural kind terms. In the case of names, for example, a causal theory of reference typically involves the following claims:
Weaker versions of the position (perhaps not properly called "causal theories"), claim merely that, in many cases, events in the causal history of a speaker's use of the term, including when the term was first acquired, must be considered to correctly assign references to the speaker's words.
Causal theories of names became popular during the 1970s, under the influence of work by Saul Kripke and Keith Donnellan. Kripke and Hilary Putnam also defended an analogous causal account of natural kind terms.
In lectures later published as Naming and Necessity, Kripke provided a rough outline of his causal theory of reference for names. Although he refused to explicitly endorse such a theory, he indicated that such an approach was far more promising than the then-popular descriptive theory of names introduced by Russell, according to which names are in fact disguised definite descriptions. Kripke argued that in order to use a name successfully to refer to something, you do not have to be acquainted with a uniquely identifying description of that thing. Rather, your use of the name need only be caused (in an appropriate way) by the naming of that thing.
Such a causal process might proceed as follows: the parents of a newborn baby name it, pointing to the child and saying "we'll call her 'Jane'." Henceforth everyone calls her 'Jane'. With that act, the parents give the girl her name. The assembled family and friends now know that 'Jane' is a name which refers to Jane. This is referred to as Jane's dubbing, naming, or initial baptism.
However, not everyone who knows Jane and uses the name 'Jane' to refer to her was present at this naming. So how is it that when they use the name 'Jane', they are referring to Jane? The answer provided by causal theories is that there is a causal chain that passes from the original observers of Jane's naming to everyone else who uses her name. For example, maybe Jill was not at the naming, but Jill learns about Jane, and learns that her name is 'Jane', from Jane's mother, who was there. She then uses the name 'Jane' with the intention of referring to the child Jane's mother referred to. Jill can now use the name, and her use of it can in turn transmit the ability to refer to Jane to other speakers.
Philosophers such as Gareth Evans have insisted that the theory's account of the dubbing process needs to be broadened to include what are called 'multiple groundings'. After her initial baptism, uses of 'Jane' in the presence of Jane may, under the right circumstances, be considered to further ground the name ('Jane') in its referent (Jane). That is, if I am in direct contact with Jane, the reference for my utterance of the name 'Jane' may be fixed not simply by a causal chain through people who had encountered her earlier (when she was first named); it may also be indexically fixed to Jane at the moment of my utterance. Thus our modern day use of a name such as 'Christopher Columbus' can be thought of as referring to Columbus through a causal chain that terminates not simply in one instance of his naming, but rather in a series of grounding uses of the name that occurred throughout his life. Under certain circumstances of confusion, this can lead to the alteration of a name's referent (for one example of how this might happen, see Twin Earth thought experiment).
Causal theories of reference were born partially in response to the widespread acceptance of Russellian descriptive theories. Russell found that certain logical contradictions could be avoided if names were considered disguised definite descriptions (a similar view is often attributed to Frege, mostly on the strength of a footnoted comment in On Sense and Reference, although many Frege scholars consider this attribution misguided). On such an account, the name 'Aristotle' might be seen as meaning 'the student of Plato and teacher of Alexander the Great'. Later description theorists expanded upon this by suggesting that a name expressed not one particular description, but many (perhaps constituting all of one's essential knowledge of the individual named), or a weighted average of these descriptions.
Kripke found this account to be deeply flawed, for a number of reasons. Notably:
A causal theory avoids these difficulties. A name refers rigidly to the bearer to which it is causally connected, regardless of any particular facts about the bearer, and in all possible worlds.
The same motivations apply to causal theories in regard to other sorts of terms. Putnam, for instance, attempted to establish that 'water' refers rigidly to the stuff that we do in fact call 'water', to the exclusion of any possible identical water-like substance for which we have no causal connection. These considerations motivate semantic externalism. Because speakers interact with a natural kind such as water regularly, and because there is generally no naming ceremony through which their names are formalized, the multiple groundings described above are even more essential to a causal account of such terms. A speaker whose environment changes may thus observe that the referents of his terms shift, as described in the Twin Earth and Swamp man thought experiments.