This volume is based on the lectures given in London as The Royal Institute of Philosophy’s annual lecture series for 2016–7. The topic chosen for the series was Metaphysics, an area where at the moment there is much exciting and innovative work being done. As will be clear from the list of authors, many of the leading figures in contemporary metaphysics are represented here. The volume thus testifies to the fruitfulness of the subject, as well as making a significant contribution to its development.

Several papers in the volume consider the nature of metaphysical explanation, its scope and limits. The currently fashionable notion of grounding is taken up by a number of our authors, while there are also papers arguing for optimism about the potential scope of metaphysical explanation and against conservative restrictions on what should be countenanced in metaphysics. The prospects for a Fregean account of number are considered, as well as the question of quantifier variance.

As would be expected, there are papers on such central metaphysical topics as essence, necessity, possibility and identity. Ranging wider, and testifying to the breadth of metaphysics as a subject, there are treatments of free will, of solipsism in Wittgenstein’s philosophy of the 1930s, of the nature of social practices, of the notion that the conceptual recommendations of metaphysics are to do with assessing and perhaps changing the way we live, and also a consideration of the ontological status of the foetus and the unborn child.

We have, unfortunately, to note with deep sadness the death in December 2017 of one of our contributors, Bob Hale. Bob was a much admired figure philosophically and personally, and while he was able to give his lecture, in the preparation of his paper for publication we have been assisted by Jessica Leech, another of our contributors, to whom we are very grateful.

On behalf of the Royal Institute of Philosophy, I would like to express thanks to all the contributors, both for their lectures, and for their written contributions, and also to Adam Ferner for compiling the index.