 In causal accounts, clause (ii) is strengthened by requiring a causal relation between the physical states: for any computational state transition of the form s1 → s2, the physical state p1 (which maps onto computational state s1) causes the system to go into physical state p2 (which maps onto computational state s2) (Chrisley 1995, Chalmers 1995, 1996, 2011, Scheutz 1999, 2001).