The target paper was intended to initiate dialogue about challenges to personality psychology's progress as a truly behavioural science, and the commentaries' diverse reactions underscore the fact that these issues do indeed merit serious discussion. This response addresses several broad questions raised in the commentaries—what is behaviour, is behaviour of primary importance yet understudied, and what are the strengths and weaknesses of core types of behavioural data? In addition, it addresses an issue raised in several commentaries, but only briefly mentioned in the target paper—the fact that behaviour can be conceptualized and measured at multiple levels of abstraction. These issues have implications for the nature of personality psychology and for the research conducted by personality psychologists. Copyright © 2009 John Wiley & Sons, Ltd.