an inconsistency is generated that entails the causal impotence of mental properties. The first principle, which most ontological physicalists would accept, is the causal closure of the physical domain, according to which, every physical effect has a sufficient physical cause. The second principle Kim notes is that of causal exclusion, which holds that no normal event can have more than one sufficient cause. The problem is that a behavior cannot have as its cause, both a physical event and a (supervening) mental event, without resulting in a case of overdetermination (thus violating the principle of causal exclusion). The result is that physical causes exclude mental states from causally contributing to the behavior. In detail: he proposes (using the chart on the right) that M1 causes M2 (these are mental events) and P1 causes P2 (these are physical events). M1 has P1 as its supervenience base, and M2 has P2 as its supervenience base. The only way for M1 to cause M2, is by causing its supervenience base P2 (a case of mental-to-physical causation). If P1 causes P2, and M1 causes P2, then we have a case of causal overdetermination. Applying the principle of causal-exclusion, either P1 or M1 must be eliminated as a cause of P2. Given the principle of the causal closure of the physical domain, M1 is excluded. The non-reductive physicalist is forced to choose between two unappealing options: one could reject the causal-exclusion principle and claim that in this scenario we are dealing with a genuine case of overdetermination, or one could embrace epiphenomenalism. Kim argues that mental causation can only be preserved by rejecting the premise of irreducibility in favor of reduction; in order for mental properties to be considered causally efficacious, they must be reducible to physical properties. Metaphysics Kim's work in metaphysics focuses primarily on events and properties. Kim developed an event identity theory, but has not defended it recently. This theory holds that events are identical if and only if they occur in the same time and place and instantiate the same property. Thus if one waves ten fingers, several events occur, including the waving of an even number of fingers, the event of waving fingers that are evenly divisible by five, and evenly divisible by ten. Some have criticized his theory as producing too many events. Kim also theorized that events are structured. He is known for a property-exemplification account of events.