 A crucial notion in metaphysics is that of one entity depending for its existence upon another entity—not in a merely causal sense, but in a deeper, ontological sense (but see Ingthorsson 2002: 96 for discussion on the idea that causal relations could be understood as one-sided existential dependence; cf. also Bennett 2017: Ch. 4, where it is argued that the line between causal and noncausal determination is not clear). The kind of dependence in question must also be distinguished from any kind of logical dependence, because logical relations, strictly speaking, cannot obtain between concrete objects, nor between abstract objects that are not propositional in nature. We should also distinguish ontological dependence, broadly conceived, from what is usually considered a stricter type of metaphysical dependence, namely metaphysical grounding. The link between ontological dependence and metaphysical grounding (or simply “metaphysical dependence”, as it is sometimes called, see Rosen 2010 and the separate entry on  metaphysical grounding;  see also Trogdon 2013 for discussion) will be discussed below, but this entry concerns a somewhat broader family of relations of dependence. The notion of ontological independence is also important, and it is often used to describe the idea that something is fundamental. This idea as well will be discussed below (but see also the separate entry on  fundamentality).