 To find the explanatory hypothesis most likely to be true, especially about something that might be unobservable, he claims to follow the example of science. Using Bayes’ Theorem, he looks for a hypothesis \(h\) such that \(p(e\mid h \amp k) \gt p(e\mid k)\) where \(p\) is probability, \(e\) is the existence of a complex universe, and \(k\) is the background data. A hypothesis is more likely to be true (1) in so far as it has high explanatory power, in that it makes probable the evidence of the observation; this may be predictive but can be postdictive as well (Swinburne 1996: 34, 2001: 80–81), and insofar as the evidence is very unlikely to occur if the hypothesis is false. And (2), it has a greater prior probability. The prior probability of a hypothesis encompasses three features: (a) how well it fits with our background knowledge (2001: 81). The broader the scope, the less relevant this criterion becomes (2004: 60). Since there are no “neighboring fields of inquiry related to the origin of the universe”, Swinburne treats this condition in the cosmological argument as irrelevant or reducing to the feature of simplicity (1996: 29). (b) The scope of the hypothesis (the extent of its claims)—the broader the scope, the less likely it is to be true. For example, all crows are black is less likely to be true than all crows along the upper Mississippi River are black. Since both scientific naturalism and theism have the same scope—explaining the universe, this does not factor into his calculations for explaining the complex universe (2001: 82); and (c) simplicity, which for Swinburne holds the key (2001: 82–83).