The purpose of this work is to provide a metaphysical theory of properties and scientific laws. This sentence will require some unpacking. By a ‘metaphysical’ theory here, I mean a theory of what exists in the world. In this investigation I am primarily concerned with a theory of what properties there are in the world and the role they play in scientific laws. This may be contrasted with a linguistic or epistemic project, as it is not primarily about our language, (...) ideas, or theorizing but rather about what is in the world itself. Properties are what we may pre-philosophically think of as the characteristics of an object: such as its height, weight, color, etc. Investigation may cause us to doubt whether some of these pre-philosophical properties are genuine in a metaphysical sense: whether or not the property is actually present as a feature of the world. By scientific laws, I mean the statements we make in the form of exceptionless generalities about the world within the sciences. Here I do not mean to evaluate how science comes about these generalizations, only that they do and how these generalizations may be grounded in a metaphysical theory of properties. The link between these two things: properties and scientific laws, comes about because our scientific laws prominently feature properties: velocity, temperature, charge, viscosity, etc. After a review of some of the theories currently proposed in the philosophical literature along with a treatment of some of the problems that arise out of these theories, I will propose a new theory. This theory, entitled ‘Constitutive Trope Theory’ is a form of a ‘bundle trope theory’ as it proposes that objects in the world are composed entirely out of particularized properties. However, rather than proposing a primitive relation that does the bundling, this theory will propose that, at least for the objects we are familiar with, properties arise out of relations between lower-level properties that instantiate them. For example, a mammal may exist because of the relationship between the organs that lead to its unique properties as a mammal. Those organs in turn exist because of relationships between their cells that lead to their unique properties as a particular kind of organ. And so on down the chain until we hit ‘foundational properties’: properties which are not dependent on any other properties for their existence. I will say very little about these properties as I do not believe that any such properties have currently been found and will argue that such theorizing is premature before such properties have been empirically identified. Following this account, I will consider some of the problems that must be overcome and some final considerations in favor of this theory over other competing theories of properties and scientific laws. (shrink)