Steve Gimbel

, Peter Achinstein argues against the long-standing claim that ‘evidence’ is ambiguous in possessing a sense of confirming evidence and a sense of supporting evidence. He argues that explications of supporting evidence will necessarily violate his contentions that evidence is a discontinuous ‘threshold concept’ and that any philosophical account of supporting evidence will be too weak to be useful to working scientists. But an account of supporting evidence may be formulated which includes Achinstein's notion of epistemic thresholds that finds examples in Achinstein's own historical case studies. Thresholds and the denial of ambiguity Achinstein's new account of confirming evidence Achinstein's argument against the ‘ambiguity response’ A threshold-based approach for restoring the ambiguity Maxwell and ‘a subject of rational curiosity’ Bohr and ‘future development of our understanding’ Perrin and the edge of reasonable belief Restoring ambiguity.

This paper describes an argumentative fallacy we call ‘Retroductive Analogy.’ It occurs when the ability of a favored hypothesis to explain some phenomena, together with the fact that hypotheses of a similar sort are well supported, is taken to be sufficient evidence to accept the hypothesis. This fallacy derives from the retroductive or abductive form of reasoning described by Charles Sanders Peirce. According to Peirce’s account, retroduction can provide good reasons to pursue a hypothesis but does not, by itself, provide good reasons to believe the hypothesis. In successful applications of retroduction, pursuit leads to the accumulation of evidence. In retroductive analogy, comparison with other successful hypotheses is substituted for the genuine pursuit of evidence. We describe a case from ecological genetics in which retroduction plays a legitimate role as the initial phase of an ongoing research program that serves to accumulate genuine evidence for a hypothesis. We also examine two contexts in which the fallacy of retroductive analogy occurs: in defenses of Intelligent Design Theory and in defense of some hypotheses in Evolutionary Psychology