Online research in philosophy

We explore the evidential relationships that connect two standard claims of modern evolutionary biology. The hypothesis of common ancestry (which says that all organisms now on earth trace back to a single progenitor) and the hypothesis of natural selection (which says that natural selection has been an important influence on the traits exhibited by organisms) are logically independent; however, this leaves open whether testing one requires assumptions about the status of the other. Darwin noted that an extreme version of adaptationism would undercut the possibility of making inferences about common ancestry. Here we develop a converse claim—hypotheses that assert that natural selection has been an important influence on trait values are untestable unless supplemented by suitable background assumptions. The fact of common ancestry and a claim about quantitative genetics together suffice to render such hypotheses testable. Furthermore, we see no plausible alternative to these assumptions; we hypothesize that they are necessary as well as sufficient for adaptive hypotheses to be tested. This point has important implications for biological practice, since biologists standardly assume that adaptive hypotheses predict trait associations among tip species. Another consequence is that adaptive hypotheses cannot be confirmed or disconfirmed by a trait value that is universal within a single species, if that trait value deviates even slightly from the optimum. 1 Two Darwinian hypotheses 2 Logical independence 3 How adaptive hypotheses bear on the tree of life hypothesis 4 How the tree of life hypothesis bears on adaptive hypotheses 5 What do adaptive hypotheses predict? 6 Common ancestry and quantitative genetics to the rescue 7 Conclusion.

The role of Professor McLaughlin's sceptic is to introduce certain 'sceptical hypotheses', hypotheses which imply the falsity of most of what we believe about the world. Professor McLaughlin asks whether these hypotheses are coherent and thus whether they can tell us anything about what are entitled to believe, or to claim to know. He concludes that, semantic externalism notwithstanding, these hypotheses are both coherent and threatening. I shall not question this conclusion but I do wonder whether the fate of scepticism hangs entirely on the coherence of the sceptical hypotheses.

Crupi et al. (2008) offer a confirmation-theoretic, Bayesian account of the conjunction fallacy—an error in reasoning that occurs when subjects judge that Pr( h 1 & h 2 | e ) > Pr( h 1 | e ). They introduce three formal conditions that are satisfied by classical conjunction fallacy cases, and they show that these same conditions imply that h 1 & h 2 is confirmed by e to a greater extent than is h 1 alone. Consequently, they suggest that people are tracking this confirmation relation when they commit conjunction fallacies. I offer three experiments testing the merits of Crupi et al.’s account specifically and confirmation-theoretic accounts of the conjunction fallacy more generally. The results of Experiment 1 show that, although Crupi et al.’s conditions do seem to be causally linked to the conjunction fallacy, they are not necessary for it; there exist cases that do not meet their three conditions in which subjects still tend to commit the fallacy. The results of Experiments 2 and 3 show that Crupi et al.’s conditions, and those offered by other confirmation-theoretic accounts of the fallacy, are not sufficient for the fallacy either; there exist cases that meet all three of CFT’s conditions in which subjects do not tend to commit the fallacy. Additionally, these latter experiments show that such confirmation-theoretic conditions are at best only weakly causally relevant to the presence of the conjunction fallacy. Given these findings, CFT’s account specifically, and any general confirmation-theoretic account more broadly, falls short of offering a satisfying explanation of the presence of the conjunction fallacy.

A law about frequencies would be a law of nature that imposes a constraint on one or more (actual, global) frequencies. On any of the leading philosophical approaches to laws of nature, there could be laws about frequencies. Hypotheses that posit laws about frequencies turn out to behave very similarly to hypotheses that posit corresponding laws about probabilities or chances -- they make the same predictions, provide similar explanations, and are confirmed or disconfirmed by empirical evidence in the same ways. This makes it interesting to consider the possibility of interpreting probabilistic laws from scientific theories as laws about frequencies. This is surprising proposal, but I argue that the resulting view (which I call 'nomic frequentism') is able to overcome all of the standard objections to frequentist interpretation of objective probabilities.

This paper considers the relationship between G. H. von Wright's solution to the paradoxes of confirmation and his "Principal Theorem of Confirmation". The former utilizes the order of our knowledge of the qualities of confirming instances of an hypothesis; the latter states the way in which an instance contributes to the probability of an hypothesis. It is shown that these two, as stated by von Wright, are logically incompatible. Then the most thorough possible emendation of the paradoxes solution is considered, and it is shown that this still prohibits use of the "Principal Theorem" to confirm hypotheses stating necessary causal conditions, and to confirm by deliberate experiment hypotheses stating sufficient causal conditions. It is concluded that any solution of the paradoxes must rest solely upon the relation of the data to the hypothesis involved.

General Relativity and the Standard Model often are touted as the most rigorously and extensively confirmed scientific hypotheses of all time. Nonetheless, these theories appear to have consequences that are inconsistent with evidence about phenomena for which, respectively, quantum effects and gravity matter. This paper suggests an explanation for why the theories are not disconfirmed by such evidence. The key to this explanation is an approach to scientific hypotheses that allows their actual content to differ from their apparent content. This approach does not appeal to ceteris-paribus qualifiers or counterfactuals or similarity relations. And it helps to explain why some highly idealized hypotheses are not treated in the way that a thoroughly refuted theory is treated but instead as hypotheses with limited domains of applicability.

Recent discussion of the problem of the conclusive falsification of scientific hypotheses has generally regarded the Duhemian Thesis (D-Thesis) as both true and interesting [10] but has dismissed the claim that disconfirmed hypotheses can be retained in explanations of the disconfirming evidence as either trivial [3] or unargued [12]. This paper rejects these positions. First, the status, in the argument for the D-Thesis, of the claim that auxiliary assumptions are necessary for the derivation of evidential propositions from hypotheses is examined. It is concluded that depending on this status, the D-Thesis is either trivially true or unargued. Then the retention of contextually disconfirmed hypotheses is discussed. It is found that the use of such hypotheses in explanations of the disconfirming evidence is mediated by principles of scientific methodology. A new thesis is presented connecting the problem of conclusive falsification with changes in methodology. The argument for this thesis introduces a new analysis of methodological principles as inductive generalizations from scientific practice. Finally, the contribution of this analysis to the understanding of scientific change is described.

Confirmation theory is the study of the logic by which scientific hypotheses may be confirmed or disconfirmed, or even refuted by evidence. A specific theory of confirmation is a proposal for such a logic. Presumably the epistemic evaluation of scientific hypotheses should largely depend on their empirical content – on what they say the evidentially accessible parts of the world are like, and on the extent to which they turn out to be right about that. Thus, all theories of confirmation rely on measures of how well various alternative hypotheses account for the evidence.1 Most contemporary confirmation theories employ probability functions to provide such a measure. They measure how well the evidence fits what the hypothesis says about the world in terms of how likely it is that the evidence should occur were the hypothesis true. Such hypothesis-based probabilities of evidence claims are called likelihoods. Clearly, when the evidence is more likely according to one hypothesis than according to an alternative, that should redound to the credit of the former hypothesis and the discredit of the later. But various theories of confirmation diverge on precisely how this credit is to be measured?

Naive deductive accounts of confirmation have the undesirable consequence that if E confirms H, then E also confirms the conjunction H & X, for any X—even if X is utterly irrelevant to H (and E). Bayesian accounts of confirmation also have this property (in the case of deductive evidence). Several Bayesians have attempted to soften the impact of this fact by arguing that—according to Bayesian accounts of confirmation— E will confirm the conjunction H & X less strongly than E confirms H (again, in the case of deductive evidence). I argue that existing Bayesian “resolutions” of this problem are inadequate in several important respects. In the end, I suggest a new‐and‐improved Bayesian account (and understanding) of the problem of irrelevant conjunction.

Can some evidence confirm a conjunction of two hypotheses more than it confirms either of the hypotheses separately? We show that it can, moreover under conditions that are the same for nine different measures of confirmation. Further we demonstrate that it is even possible for the conjunction of two disconfirmed hypotheses to be confirmed by the same evidence.