A subject index covering "all major philosophy journals . . . and related interdisciplinary publications. All English language books and some books in other languages are also indexed." Its coverage is from 1940 to the present.
A free web resource still in process. From the site: "The [SEP] is a dynamic reference work and is a publishing project of the Metaphysics Research Lab at the Center for the Study of Language and Information (CSLI) at Stanford.