Putting Properties First considers the metaphysics of natural science. It develops and defends a contemporary metaphysical theory of natural modality called 'Modal Platonism', which puts properties first in the metaphysical hierarchy. According to this theory, natural properties-such as mass and charge-are fundamental entities which ground the laws of nature and the behavioural dispositions of physical things. This theory differs from other 'properties-first' approaches in two main ways. First, it views properties as Platonic universals, which exist even if they are not instantiated by anything. Second, the theory rejects the popular idea that properties are identical with, or essentially dependent upon, dispositions. Instead, Modal Platonism views properties as qualities which necessarily ground dispositions and other modal phenomena. This theory solves a range of philosophical puzzles regarding dispositions and laws. Given that laws of nature are a necessary precondition for scientific enquiry, Modal Platonism promises to provide a plausible metaphysical framework for all natural science.