In his new book, Alexander Bird brings together many of his important contributions to the recent debate on the metaphysical status of natural properties and laws of nature. The result is a powerful and detailed theory according to which the fundamental natural properties are ‘potencies’: they have a dispositional essence, in the sense that what has such a property is necessarily disposed to evolve in certain ways. It follows from this account that the laws of nature are necessary. Laws are relations among properties that flow from their dispositional essences; if it is essential to the property of being...