 The Intrinsic Dispositions Thesis (for short, IDT), the thesis that dispositions are intrinsic properties of their bearers, has been routinely accepted by many philosophers like Harré (1970), Armstrong (1973), Mellor (1974), Mackie (1977), Bird (1998), Molnar (2003), Choi (2005b), and Menzies (2009). Accepting it, Lewis (1997) says, ‘if two things (actual or merely possible) are exact intrinsic duplicates (and if they are subject to the same laws of nature) then they are disposed alike’ (p. 147). Lewis’s qualification about the laws of nature is important, at least for those who take the laws to be contingent, for without it IDT is scarcely plausible. If the laws are contingent then a fragile glass has intrinsic duplicates that are not disposed to break when struck. Some of them will inhabit possible worlds whose laws of nature determine that, if struck, they would experience a gentle deformation temporarily and then regain its original shape. IDT, therefore, should be understood as the thesis that within any sphere of worlds with the same laws of nature, any pair of objects with the same intrinsic properties will have the same dispositions. (For discussion of the precise meaning of the intrinsicness of dispositions, see Langton &amp; Lewis 1998; Choi 2009; and Handfield 2009.)