Abstract

We have various everyday measures for identifying the presence of consciousness, such as the capacity for verbal report and the intentional control of behavior. However, there are many contexts in which these measures are difficult to apply, and even when they can be applied one might have doubts as to their validity in determining the presence/absence of consciousness. Everyday measures for identifying consciousness are particularly problematic when it comes to ‘challenging cases’—human infants, people with brain damage, nonhuman animals, and AI systems. There is a pressing need to identify measures of consciousness that can be applied to challenging cases. This paper explores one of the most promising strategies for identifying and validating such measures—the natural-kind strategy. The paper is in two broad parts. Part I introduces the natural-kind strategy, and contrasts it with other influential approaches in the field. Part II considers a number of objections to the approach, arguing that none succeeds.