This volume is based on the lectures given in London at The Royal Institute of Philosophy's annual lecture series for 2016–17. The topic chosen for the series was metaphysics, an area where at the moment there is much exciting and innovative work being done. Several papers in the volume consider the nature of metaphysical explanation, its scope and limits. There are also 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.