What is the appropriate theory of logical probability? Tooley (2008 and 2012) employs a Carnapian theory in which the basic equiprobability assumption is formulated in terms of what are called ‘structure descriptions’, and the fundamental postulate is that all structure descriptions are equally likely. But if one holds, as Tooley (1977 and 1987) does, that governing laws are logically possible, then it is clear that the fundamental equiprobability assumption needs to be formulated in terms of governing laws of nature. At present, however, no detailed formulation of such an approach to logical...