 Expositions of the argument from fine-tuning for design are typically couched in terms of probabilities (e.g., Holder 2002; Craig 2003; Swinburne 2004; Collins 2009); see also the review Manson 2009. An elementary Bayesian formulation considers the rational impact of the observation \(R\)—that the constants (and laws and boundary conditions) are right for life—on our degree of belief concerning the design hypothesis \(D\)—that there is a cosmic designer. According to standard Bayesian conditioning, our posterior degree of belief \(P^+(D)\) after taking into account \(R\) is given by our prior conditional degree of belief \(P(D\mid R)\). Analogously, our posterior \(P^+(\neg D)\) that there is no cosmic designer is given by our prior conditional degree of belief \(P(\neg D\mid R)\). By Bayes’ theorem, the ratio between the two posteriors is