Saul Kripke's Locke Lectures were delivered in Oxford in 1973. Delivered in Kripke's usual extemporaneous style, for years the lectures have only been available as a transcription that has been informally exchanged among philosophers. This volume, which publishes the lectures in book form for the first time, follows up on some of the themes on language that Kripke started to explore in his most famous work, Naming and Necessity. The first topic that Kripke examines is the relationship of naming to existence, in particular the problem of names that are empty i.e. which refer to non-existent objects such as fictional entities. The second major topic (or pair of topics) is that of speaker's reference and semantic reference. The lectures are full of philosophically rich ideas that have already been influential, and which will continue to intrigue and engage philosophers in book form.