 Clearly not all will agree with each of Lewis’s likeness claims. Anyone who denies unrestricted mereological composition, for example, will deny 2. And the defender of strong pluralism in the material constitution debate (i.e. one who defends the view that there can be all-time coincident entities) will deny 3. And some endurantists who think that ordinary material objects can have distinct parts at distinct times will deny 5. But there is a more general problem with 1, as van Inwagen has made clear (1994: 213). Consider a world w1 that contains just two simples s1 and s2. Now consider the difference between someone p1 who believes that s1 and s2 compose something and someone p2 who does not. Ask: how many objects do p1 and p2 believe there to be in w1? The answer, it seems, is that p1 believes that there are three things and p2 only two. So how can a commitment to the existence of fusions be ontologically innocent? One recent suggestion is that although a commitment to the existence of fusions is not ontologically innocent, it almost is: to commit oneself to fusions is to commit oneself to further entities, but because they are not fundamental entities they are not ones that matter for the purpose of theory choice (Cameron 2014, Schaffer 2008, Williams 2010, and see also Hawley 2014).