 Colin Howson cites with approval the Keynesian dissolution (1988: 382) and provides the following illustration: consider h and \(h'\) which are rival explanatory frameworks. \(h'\) independently predicts e; h does not entail e but has a free parameter which is fixed on the basis of e to produce \(h(a_{0})\)—this latter hypothesis thus entails e. So \(h'\) predicts e while \(h(a_{0})\) merely accommodates e. Let us assume that the prior probabilities of h and \(h'\) are equal (i.e., \(p(h) = p(h')\)). Now it stands to reason that \(p(h(a_0)) \lt p(h)\) since \(h(a_{0})\) entails h but not vice versa—thus Howson shows it follows that the effect of e’s confirmation will be to leave \(h'\) no less probable—and quite possibly more probable—than \(h(a_{0})\) (1990: 236–7). Thus predictivism appears true but the operating factor is the role of unequal prior  probabilities.[14] 