 Emergence may differ with respect to the strength of these two modal correlations. Accounts of weak emergence typically specify the necessity as metaphysical necessity (absolute or unconditional necessity), indicating that emergent phenomena are (in a somewhat hazy sense) “nothing over and above” their subvening base phenomena. Accounts of strong emergence specify it as (merely) nomological necessity (conditional on the holding of relevant laws of nature), indicating a greater ontological distinctness between emergent features and their bases. Indeed, it has sometimes been suggested that the difference between strong and weak varieties of emergence is best understood in terms of the distinction between merely nomological and metaphysical supervenience (Chalmers 1996, Noordhof 2010).