 In many experimental contexts, the underlying idea is causal necessity and sufficiency. However, if \(A=B\), then A’s presence is also necessary and sufficient for B’s presence since they are identical. Thus, a brain lesion that eliminates N and thereby eliminates conscious state S might do so either because N is causally necessary for S or because \(N=S\). An intermediate relation is that N constitutes or grounds S which does not imply that \(N=S\) (see the entry on  metaphysical grounding).  Whichever option holds for S, the first step is to find N, a neural correlate of consciousness  (section 1.6).