A "Supplement" volume, edited by Donald M. Borchert, was added to the reprinted first edition in 1996, containing articles on developments in philosophy since 1967, covering new subjects and scholarship updates or new articles on those written about in the first edition.
A second edition, also edited by Borchert, was published in ten volumes in 2006 by Thomson Gale. Volumes 1–9 contain alphabetically ordered articles. Volume 10 consists of:
Appendix (pp. 1–48), containing updates and additions to the articles in the preceding volumes;