 The second objection, proffered in van Fraassen 1989 (Ch. 6), is levelled at probabilistic versions of abduction. The objection is that such rules must either amount to Bayes’ rule, and thus be redundant, or be at variance with it but then, on the grounds of Lewis’ dynamic Dutch book argument (as reported in Teller 1973), be probabilistically incoherent, meaning that they may lead one to assess as fair a number of bets which together ensure a financial loss, come what may; and, van Fraassen argues, it would be irrational to follow a rule that has this feature.