 In §1 we consider some most fundamental themes, including the main motivations and arguments for including properties in one’s ontology. In §2 we deal with the central topic of what it is for properties to be exemplified. In §3 we tackle the intertwined issues of the existence and identity conditions for properties. In §4 we consider different senses in which properties may be structurally complex. In §5 we survey the frequent appeal to properties in current metaphysics of science. In §6 we conclude with a review of formal accounts of properties and their applications in natural language semantics and the foundations of mathematics, which provide additional motivations for an ontological commitment to properties.