The term “seizure” underscores two fundamental characteristics of epileptic phenomena: they are sudden and unexpected deviations from the normal function of the nervous system. Thus 2 important criteria for a candidate convulsant mechanism are that the mechanism is compatible with normal neural functioning, and that the mechanism can produce rapid deviations from normal function. For example, the blockade of GABA-mediated inhibition is a robust and frequently studied experimental convulsant mechanism,26,28 but is unlikely to underlie human epilepsy because it is not compatible with normal function nor is it capable of sudden transitions from normal function. Of course, we can modify the GABA-block hypothesis to incorporate the “sudden and unexpected” criterion by proposing that the sudden and unexpected features arise from the condition that imposes the reduction in GABA efficacy.