 Both  (AI)  and  (RI)  could be understood as putting forward the idea that fundamental reality needs a relational underpinning (on the notion of a relational underpinning, compare Fine 2001: 25). In other words, whatever fundamentality amounts to, it must be the case that one (or several) of the various relations of metaphysical dependence may be used to define fundamentality. But since (RI) leaves completely open which of the metaphysical dependence relations are in fact relevant to fundamentality, we should mention some examples. At one point in the early 2000s, it may have been the case that most philosophers using the notion of fundamentality had in mind what we might call mereological fundamentality whereby the relevant kind of dependence is mereological dependence (see especially Schaffer 2003). A concise definition of mereological dependence is offered by Kim: 