 Given that there are good reasons to exclude some notions of dependence, such as modal dependence and perhaps causal dependence, it would appear that there is an additional question about why only some notions of dependence are such that we want to define a corresponding notion of fundamentality for them. There is an obvious challenge for the view that we should postulate several relativized notions of fundamentality. The challenge is simply that the notion of fundamentality would seem to do little in addition to the various relativized notions of (in)dependence. Indeed, this is likely to cause confusion, because the notion of fundamentality is sometimes used in the literature without any mention of which relativized sense of independence is in question. Moreover, since different types of metaphysical dependence have different formal properties (e.g., some are strict partial orders, but some might be symmetric, reflexive or non-transitive) and they can perhaps even run in different directions, it is difficult to see what could unify the different notions of fundamentality, i.e., the proper subset of those dependence relations that we consider to be relevant for  fundamentality.[10]