"In both ordinary and scientific inquiry we often seem to attribute properties to things, or to kinds of things: we say, for example, that grass is green, that the earth is spherical, that humans are animals, and that murder is wrong. We also seem to think that these properties are things in their own right: there is something that it is to be green, or spherical, or an animal, or wrong, and that scientific or normative projects are engaged in uncovering the essences of such properties.If we take these initial thoughts to amount to anything, an important question arises: what kind of things should we take properties to be? Perhaps we should take them to be those things in virtue of which one kind of thing is demarcated from another kind of thing. Or perhaps as those aspects of an object which ground the causal powers of that object. Alternatively, perhaps we should take properties to be just those things that are referred to by our predicates.These suggestions are all brief expressions of different ways of understanding properties, ranging from the thought that properties should only be those things that ground some genuine similarities between objects, thus rendering properties relatively sparse, to the thought that any predicate with consistent rules for its application can give rise to a corresponding property, thus rendering properties abundant.This project outlines and argues for pluralism about properties. It argues that we should take the existence of properties seriously, and aims to give a fully developed inventory of the various kinds of properties we should posit, why we should posit them, and what jobs each kind of property can do. It also aims to show why adopting a pluralist conception of properties over a monist conception of properties – which claims that there is only one kind of property – has significant theoretical benefits, and investigates the connections between properties and the closely related concepts of reference, truth and realism."