I argue that contemporary theories of physics are best understood as involving a more refined identity relation than the one found in first order logic. I use this identity relation to provide novel interpretations of Yang–Mills theory and General Relativity, two of the most successful physical theories. I show that my interpretation is superior to those currently on the market because it solves problems left open by extant interpretations and provides a better explanation of the distinctive features of these theories. My interpretation also fills gaps in justification found in the physics literature.

Here I discuss three different problems in science which can be advanced using philosophical tools. In each case I engage heavily with the science, drawing on the current state of play for the field, with the goal of providing helpful guidance to scientists and policy-makers.

The first chapter looks at the risks associated with a newly developing invasive species control method - gene-drives, arguing that we can warrant certain harms by weighing up the damages against the potential benefits we might see on a global scale. Here I use techniques and ideas from applied ethics and policy to show that certain highly-damaging species, including European rabbits and ship rats, are viable targets for the technique despite the risk of their global extermination.

The second dives into political theory, intervening on a long and complicated debate surrounding the mechanisms behind the theory of the democratic peace. Here I use concepts like conceptual engineering, over-determination, and a newly proposed argument for the reliability of science called ‘the tangle’, developed by myself, Cartwright, Hardie, Montuschi and Soleiman, to argue that there is no single mechanism, but instead many which work together to secure the reliability of the democratic peace.

The third and final chapter points out a worrying trend of scientists and policy-makers thinking that the potential harms of science arise almost exclusively out of the application of research, rather than the research itself. Using tools fromanalytic philosophy I dive into the harms research can cause, proposing a new categorisation of these harms for use when creating moratoriums and bans. This categorisation system is then use on a real world case - research into the ‘gay gene’ - to show how it can help determine the most effective ways to mitigate harms via controlling what science can study.

This dissertation is an investigation of the conceptual and physical foundations of cosmological inflation. Cosmologists have long claimed that inflation solves certain fine-tuning problems with the previous standard model of cosmology, the highly successful big bang model of the universe. The major contributions of the dissertation are an analysis and a critique of the arguments cosmologists could be construed as making to support this claim, arguments which have been taken as the standard rationale for the initial (and even continuing) widespread acceptance of inflation in cosmology. There are four chapters. In the first I establish the context of the investigation by clarifying the notion of a cosmological model (the central component of which is a relativistic spacetime) and explaining important features of the cosmological models underlying the big bang model. In the second chapter I analyze and criticize the aforementioned standard motivation for the inclusion of inflation in modern cosmological models and address the question of whether inflation solves the big bang model's fine-tuning problems. The main conclusion of this chapter is that there is at present no good argument that inflation solves the big bang model's fine-tuning problems. In chapters three and four I delve deeper into the fine-tuning argument apparently favored by cosmologists, namely the one that depends on interpreting fine-tuning in terms of probabilities or likelihoods. In chapter three I show how probabilities are implemented, interpreted, and justified in classical statistical physics, introducing a novel interpretation of statistical mechanics along the way. In the final chapter I put the formal implementations, the interpretations, and the justification of probability from chapter three to work in the context of cosmology. I ultimately claim that the many challenges I raise in the chapter are decisive for current and even forseeable approaches to defining cosmological probabilities.

Physicists have historically taken the concepts of classical thermodynamics to be universally applicable, well-understood, and secure. Thus Eddington’s famous proclamation that “the law that entropy always increases, holds, I think, the supreme position among the laws of Nature”, and that “if your theory is found to be against the second law of thermodynamics, Ican give you no hope; there is nothing for it but to collapse in deepest humiliation.” (1928, 74) Somewhat more cautiously, Einstein remarked that “[classical thermodynamics] is the only physical theory of universal content which I am convinced will never be overthrown, within the framework of applicability of its basic concepts.” (1946, 33) Suffice to say, classical thermodynamics is accorded a special status few other physical theories could dream of having. This can still be observed in contemporary physics, where classical thermodynamic concepts are typically borrowed wholesale and applied into new domains like black hole physics and quantum gravity research by physicists like Bekenstein, Hawking, and others.

My task here is to subject this faith in classical thermodynamics to philosophical scrutiny. What is the ‘framework of applicability’ for thermodynamic concepts, and what are its limits? In this vein, my dissertation critically examines and challenges the foundations of thermodynamics by studying the historical trajectory of classical thermodynamic concepts and their justifications, as well as the extent to which these justifications can be carried over to new domains of inquiry. In particular, I survey how classical thermodynamic concepts extend into the domains of information theory, quantum mechanics, special relativity, general relativity, and quantum gravity. I argue that the ‘framework of applicability’ of classical thermodynamic concepts is more limited than typically assumed, and more open questions remain in the foundations of thermodynamics than one might expect.