Richard Dawid

The No Alternatives Argument

Scientific theories are hard to find, and once scientists have found a theory, H, they often believe that there are not many distinct alternatives to H. But is this belief justified? What should scientists believe about the number of alternatives to H, and how should they change these beliefs in the light of new evidence? These are some of the questions that we will address in this article. We also ask under which conditions failure to find an alternative to H confirms the theory in question. This kind of reasoning (which we call the ‘no alternatives argument’) is frequently used in science and therefore deserves a careful philosophical analysis. 1 Introduction 2 The Conceptual Framework 3 The No Alternatives Argument 4 Discussion I: A Quantitative Analysis of the No Alternatives Argument 5 Discussion II: The Number of Alternatives and the Problem of Underdetermination 6 Conclusions Appendix A  Appendix B  1 Introduction 2 The Conceptual Framework 3 The No Alternatives Argument 4 Discussion I: A Quantitative Analysis of the No Alternatives Argument 5 Discussion II: The Number of Alternatives and the Problem of Underdetermination 6 Conclusions Appendix A  Appendix B  Appendix A  Appendix B 

Underdetermination and Theory Succession from the Perspective of String Theory

This article investigates the implications of string theory for the conception of scientific theory confirmation. The classical understanding of theory confirmation is based on the assumption that scientific theory building is underdetermined by the available empirical data. Several arguments are presented, which suggest a devaluation of this ‘principle of scientific underdetermination’ in the context of string theory. An altered conception of scientific progress emerges that is not based on the notion of theory succession.

Scientific Realism in the Age of String Theory

String theory currently is the only viable candidate for a unified description of all known natural forces. This article tries to demonstrate that the fundamental structural and methodological differences that set string theory apart from other physical theories have important philosophical consequences. Focussing on implications for the realism debate in philosophy of science, it is argued that both poles of that debate face new problems in the context of string theory. On the one hand, the claim of underdetermination of scientific theory by the available empirical data, which is a pivotal element of empiricism, loses much of its plausibility. On the other hand, the dissolution of any meaningful notion of an external ontological object destroys the basis for conventional versions of scientific realism. String theory seems to suggest an intermediate position akin to Structural Realism that is based on a newly emerging principle, to be called the principle of theoretical uniqueness.

On the Conflicting Assessments of the Current Status of String Theory

The current status of string theory is assessed quite differently by most of the theory’s exponents than by the majority of physicists in other fields. While the former tend to have a high degree of trust in string theory’s viability, the latter largely share a substantially more skeptical point of view. This article argues that the controversy can be best understood in terms of a paradigmatic rift between the two sides over their understandings of theory assessment. An attempt is made to evaluate the two conflicting paradigms on their own terms.

Higgs Discovery and the Look Elsewhere Effect

The discovery of the Higgs particle required a signal of 5σ significance. The rigid application of that condition is a convention that disregards more specific aspects of the given experiment. In particular, it does not account for the characteristics of the look elsewhere effect in the individual experimental context. The paper relates this aspect of data analysis to the question as to what extent theoretical reasoning should be admitted to play a role in the assessment of the significance of empirical data.

Many worlds: decoherent or incoherent?

We claim that, as it stands, the Deutsch–Wallace–Everett approach to quantum theory is conceptually incoherent. This charge is based upon the approach’s reliance upon decoherence arguments that conflict with its own fundamental precepts regarding probabilistic reasoning in two respects. This conceptual conflict obtains even if the decoherence arguments deployed are aimed merely towards the establishment of certain ‘emergent’ or ‘robust’ structures within the wave function: To be relevant to physical science notions such as robustness must be empirically grounded, and, on our analysis, this grounding can only plausibly be done in precisely the probabilistic terms that lead to conceptual conflict. Thus, the incoherence problems presented necessitate either the provision of a new, non-probabilistic empirical grounding for the notions of robustness and emergence in the context of decoherence, or the abandonment of the Deutsch–Wallace–Everett programme for quantum theory.

Bayesian perspectives on the discovery of the Higgs particle

It is argued that the high degree of trust in the Higgs particle before its discovery raises the question of a Bayesian perspective on data analysis in high energy physics in an interesting way that differs from other suggestions regarding the deployment of Bayesian strategies in the field.

The No Miracles Argument without the Base Rate Fallacy

According to an argument by Colin Howson, the no-miracles argument (NMA) is contingent on committing the base-rate fallacy and is therefore bound to fail. We demonstrate that Howson’s argument only applies to one of two versions of the NMA. The other version, which resembles the form in which the argument was initially presented by Putnam and Boyd, remains unaffected by his line of reasoning. We provide a formal reconstruction of that version of the NMA and show that it is valid. Finally, we demonstrate that the use of subjective priors is consistent with the realist implication of the NMA and show that a core worry with respect to the suggested form of the NMA can be dispelled.

A speculative remark on holography

Abstract Holography suggests a considerable reduction of degrees of freedom in theories with gravity. However it seems to be difficult to understand how holography could be realized in a closed re-contracting universe. In this Letter we claim that a scenario which achieves that goal will eliminate all spatial degrees of freedom. This would require a different concept of quantum mechanics and would imply an intriguing increase of power for the natural laws.

Propagating Higgs bound states in SUSY

Abstract The possibilities for an underlying theory behind an effective supersymmetric Nambu-Jona-Lasinio like model of electroweak symmetry breaking with propagating Higgs bound states (e.g. supersymmetric topcondensation) are investigated. The concept of a renormalizable underlying theory turns out not to be appropriate. We argue that the new theory should come from the Planck scale and be connected to supergravity. Such a model can be constructed but necessarily implies a nonlinear definition of the full Lagrangian.