 Metaphysical realism is the thesis that the objects, properties and relations the world contains, collectively: the structure of the world [Sider 2011], exists independently of our thoughts about it or our perceptions of it. Anti-realists either doubt or deny the existence of the structure the metaphysical realist believes in or else doubt or deny its independence from our conceptions of it. Realists about numbers, for example, hold that numbers exist mind-independently. This view is opposed by Nominalists who deny the existence of abstract objects and Intuitionists who agree numbers exist, but as mental constructions, denying their mind-independence. Some realists about laws of nature, to take an empirical example, hold that laws are relations between universals [Armstrong 1983], others that laws are ontologically primitive entities [Maudlin 2007]. Anti-realists about laws of nature, on the other hand, either deny there are any laws at all [Cartwright 1983; van Fraassen 1989] or else discern a dependence on human concepts in the nature of these laws, interpreting them as expressing certain expectations we have about regularities that we unconsciously project onto the world [Blackburn 1986]. 