 There have also been attempts to argue for abduction in a more straightforward fashion, to wit, via enumerative induction. The common idea of these attempts is that every newly recorded successful application of abduction—like the discovery of Neptune, whose existence had been postulated on explanatory grounds (see Section 1.2)—adds further support to the hypothesis that abduction is a reliable rule of inference, in the way in which every newly observed black raven adds some support to the hypothesis that all ravens are black. Because it does not involve abductive reasoning, this type of argument is more likely to also appeal to disbelievers in abduction. See Harré 1986, 1988, Bird 1998 (160), Kitcher 2001, and Douven 2002 for suggestions along these lines.