Mumford is the sole-author of four books: Dispositions (1998), Laws in Nature (2004), David Armstrong (2007), and Watching Sport: Aesthetics, Ethics and Emotions (2011).
After a return to the field, following a self-imposed absence, he was working on a book (Powers) and continued up until his sudden and untimely death in August 1999.
[4] Mumford, along with several other figures in the field of metaphysics, including David Armstrong, were involved collaboratively in providing insight on Molnar's work, and on him as a person, but the editing was left to Mumford, as was the writing of an introductory chapter to correctly present and establish the material laid out - something which Molnar did not get round to doing before his death.
This time, however, it was through mutual friend Tony Skillen (lecturer in philosophy at the University of Kent) on behalf of Molnar's former partner Carlotta McIntosh, who had given access to the manuscript and who shared it with Mumford.
Mumford worked alongside Alexander Bird (Bristol)[8][9] and Helen Beebee (Birmingham)[10] within this project with their joint focus on "causes, laws, kinds, and dispositions".
This project explored how, or whether, all these distinct notions – law, cause, natural kind, disposition – can be made to fit together into a coherent and unified worldview.