Penelope Mackie, a philosopher at the University of Nottingham, has died. The following obituary was provided by Mark Jago (Nottingham). It is with great sadness that we announce the death of our friend and colleague, Penelope Mackie, following a period of illness. Penelope was born into an academic family. Her paternal grandfather Alexander was professor of education at the University of Sydney, and her father was the philosopher J.L. Mackie (whose philosophical papers she co-edited). She went to Somerville College, Oxford, in 1971, where she took the BPhil in Philosophy with a thesis, Identity and Continuity, in 1978, and later the DPhil in 1987, with a thesis, How Things Might Have Been: A Study in Essentialism. After her DPhil, Penelope moved to the US, first as a visiting lecturer at the University of Maryland (1986–1987) and then as Assistant Professor of philosophy at Virginia Commonwealth University (1987–1990). She then returned to Oxford, this time as a fellow of New College (1990–1994), before moving to Birmingham in 1994 and then to Nottingham in 2004, where she worked until her death. Penelope’s philosophical interests were broad, including ancient Greek philosophy, early modern philosophy (particularly Berkeley and Hume), free will, causation, essence and modality, identity, and the metaphysics of material objects. Her best-known work is her 2006 book, How Things Might Have Been. In it, she defends the view that objects have bare identities. A person, or any other object, simply is the thing it is and could not have been any other, although it could have been some radically different kind of thing. You could have been a toadstool, or the number seven, and still remained you, she argued. Reviewers praised the book as ‘one of the clearest and fullest discussions of contemporary essentialism that has appeared for quite some time’. The clarity and carefulness of Penelope’s philosophical work was also consistently applied to her teaching and administrative duties. She was renowned among colleagues for her meticulousness, carefulness, and diligence, including during her tenure as Head of Department at Nottingham from 2007 to 2010. These high standards were also demonstrated in her teaching. Penelope’s comments on student essays were legendary, sometimes nearing the word-count of the essay itself. She was a staunch..