 It often seems very natural to use modal terminology when talking about the laws of nature. We are inclined to say that nothing can move faster than light to express the fact that the laws rule out superluminal motion, and to state Newton’s First Law by saying that an object cannot depart from uniform rectilinear motion unless acted on by an external force. This motivates the thought that there is a form of necessity associated with the natural  laws.[8]  It is controversial, however, whether that form of necessity is simply metaphysical necessity, or another kind of necessity. The former view is taken by necessitarians (Swoyer 1982; Shoemaker 1980, 1998; Tweedale 1984; Fales 1993; Ellis 2001; Bird 2005), who believe that the laws (or the laws conditionalized on the existence of the properties mentioned in them) are metaphysically necessary. Contingentists deny that, but many contingentists hold that there is a kind of necessity distinct from metaphysical necessity that is characteristic of the laws (e.g., Fine 2002), and which may be called natural or nomic necessity. It is often assumed that nomic necessity is a weaker form of necessity than metaphysical necessity: it attaches to the laws and to all truths that are metaphysically necessitated by them, so that anything that is metaphysically necessary is also nomically necessary, but not vice versa.