Ravi asked:

What did Kripke achieve in his rigid designator theory? Why are logically proper names rigid
designators?

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The theory of rigid designators is a challenge to the descriptive theories of reference which basically
hold that there is a sense or description under which a person is known and this description
determines which person you are referring. According to a descriptive theory, you may know Aristotle
as the philosopher who taught Alexander the Great and this description, or sense, determines the
reference. However, Kripke points out that Aristotle may not have taught Alexander. When we talk
about Aristotle as having done otherwise, we still mean the man Aristotle. Only if we can refer to
Aristotle without any particular description can we make sense of saying what he may and may not
have done. Aristotle as a rigid designator picks out Aristotle in "all possible worlds" and we can talk
about Aristotle as having had a completely different life than the one he did.

Kripke is able to explain the fact that we may know of someone and refer to him even when we
possess a false description. We may know Gödel as "the man who discovered the incompleteness of
arithmetic" and this may be the only thing we know about him. On the description theory, if Schmidt
really made this discovery then if we talk about Gödel by means of the identifying description "the
man who discovered the incompleteness of arithmetic", we would identify and refer to Schmidt, who
we have never heard of and do not mean to refer to. Kripke suggests that there is a causal or
historical chain between the use of a name as a rigid designator and the person named. When we
use the term Gödel there is a chain of usage leading back to the particular man Gödel. Within this
chain false beliefs can be spread.

Kripke takes language as very much something we use, and we can use language without knowing
very much at all. Because it is difficult to deny that we use names as Kripke describes, this
constitutes a very strong challenge to any theory of names which relates a name to an essential
description or a cluster of descriptions.

Kripke has shown that necessary truth is not to be essentially related to the a priori. Kripke admits it is
a contingent truth that Hesperus (the evening star) and Phosphorus (the morning star) designate one
and the same star. We can imagine a possible world in which a man sees the evening star and sees
the morning and they turn out to be different, but this would be a world that contained not Venus, but
two distinct stars. As rigid designators both Hesperus and Phosphorus refer to the planet Venus
which is a necessary identity relation because the names have meaning by virtue of a single referent,
but this cannot be known a priori — it is an empirical discovery. Before Kripke's Naming and
Necessity,empirical truth was understood to be contingent and necessary truth was that which we
can determine without reference to the world. Kripke has shown that necessary truth is not about how
we come to know things but it is about what things we think could be different.

Rachel Browne