In principle, humour studies would be significantly enhanced by a comprehensive understanding of laughter and amusement. Members of various scientific disciplines, however, often approach laughter from distinct, rather narrow, experimental or observational paradigms, and rarely make direct challenges to broader theories that are generally accepted as incomplete, but also difficult to falsify. Evaluating, comparing, and ranking such theories is possible, however, using the concept of explanatory scope. To better establish the range of questions a comprehensive theory of laughter must resolve, the author reviewed 525 peer-reviewed journal articles and recorded a total of 852 topics addressed by the authors. These were categorized into 29 themes. The list provided should allow scholars to more effectively assess the strengths and weaknesses of existing laughter theories and help guide future endeavours to more fully understand this important behaviour.