James Ladyman

There has recently been a good deal of controversy about Landauer's Principle, which is often stated as follows: The erasure of one bit of information in a computational device is necessarily accompanied by a generation of kT ln 2 heat. This is often generalised to the claim that any logically irreversible operation cannot be implemented in a thermodynamically reversible way. John Norton (2005) and Owen Maroney (2005) both argue that Landauer's Principle has not been shown to hold in general, and Maroney offers a method that he claims instantiates the operation reset in a thermodynamically reversible way. In this paper we defend the qualitative form of Landauer's Principle, and clarify its quantitative consequences (assuming the second law of thermodynamics). We analyse in detail what it means for a physical system to implement a logical transformation L, and we make this precise by defining the notion of an L-machine. Then we show that logical irreversibility of L implies thermodynamic irreversibility of every corresponding L-machine. We do this in two ways. First, by assuming the phenomenological validity of the Kelvin statement of the second law, and second, by using information-theoretic reasoning. We illustrate our results with the example of the logical transformation 'reset', and thereby recover the quantitative form of Landauer's Principle.

The Hole Argument is primarily about the meaning of general covariance in general relativity. As such it raises many deep issues about identity in mathematics and physics, the ontology of space–time, and how scientific representation works. This paper is about the application of a new foundational programme in mathematics, namely homotopy type theory, to the Hole Argument. It is argued that the framework of HoTT provides a natural resolution of the Hole Argument. The role of the Univalence Axiom in the treatment of the Hole Argument in HoTT is clarified.

The Univalence axiom, due to Vladimir Voevodsky, is often taken to be one of the most important discoveries arising from the Homotopy Type Theory research programme. It is said by Steve Awodey that Univalence embodies mathematical structuralism, and that Univalence may be regarded as ‘expanding the notion of identity to that of equivalence’. This article explores the conceptual, foundational and philosophical status of Univalence in Homotopy Type Theory. It extends our Types-as-Concepts interpretation of HoTT to Universes, and offers an account of the Univalence axiom in such terms. We consider Awodey’s informal argument that Univalence is motivated by the principle that reasoning should be invariant under isomorphism, and we examine whether an autonomous and rigorous justification along these lines can be given. We consider two problems facing such a justification. First, there is a difference between equivalence and isomorphism and Univalence must be formulated in terms of the former. Second, the argument as presented cannot establish Univalence itself but only a weaker version of it, and must be supplemented by an additional principle. The article argues that the prospects for an autonomous justification of Univalence are promising.

Scientism is usually thought of as sinful, but it can be redeemed for our salvation. Scientism should not be dogmatic, nor should it ignore the actual limitations to current science. Other modes of inquiry deserve epistemic respect, and scientists should not be deferred to about matters beyond their expertise. However, limits should not be placed on what science can study and we cannot say in advance what the limits of future science will be. Where science conflicts with common sense, religion, and tradition, it should be regarded as authoritative for the purposes of education and public policy as well as objective inquiry; and scientific knowledge is even relevant to moral and political deliberation. This is the core of scientism. This chapter elaborates a way of thinking of scientism as a stance characterized in terms of positive and negative components and argues for a humane form of scientism.

This is the second of a pair of papers, of which the first showed how each of the main late phlogistic theories effectively reached impasses due to internal problems or included features which made them unacceptable even to other phlogistians. This paper deals with theory comparison and theory change. It gives an unprecedentedly detailed comparison between the available theories in 1790–1791, and shows that this was overwhelmingly in favour of the new chemistry. This time period correlates well with many chemists changing to the new theory. There was a plurality of views held by individuals and there was freedom of individual choice concerning theories, yet there was also a widespread and rational change to the new chemistry.

Whether we think of the routine conviction or acquittal of suspects on the basis of scientific evidence in the law courts, the trust placed in scientific medicine and the extraordinary interventions it makes possible, or the importance that policy makers attach to the opinions of scientists, it is clear that those making up our scientific institutions are among the most authoritative and respected people that there are. Among intellectual endeavours science has an unrivalled dominance in terms of funding, status and influence on practical affairs. However, the days when natural science was widely considered to be a model for the study of the arts and the humanities already seem distant. Indeed the influence of science even within subjects which were conceived of as scientific from their very inception, such as political science and sociology, has waned considerably. Perhaps in economics scientism is still dominant but elsewhere in academia a widespread disillusionment with science has taken hold. Perhaps this is understandable given what were with hindsight the obviously foolish attempts to study everything with the same methodology as is employed in physics. Yet the backlash against a misconceived scientism and reductionism in the study of social life and culture has amounted to more than just a defence of disciplinary boundaries, for critics of science now assail it in its own castles (which they allege are built in the air).

This is the first of a pair of papers. It focuses on the development of the most notable phlogistic theories during the period 1766–1791, including the main experiments that their proponents proposed them to interpret. There was a rapid proliferation of late phlogistic theories, particularly from 1784, and the accounts of composition and important implications of the main theories are set out and their issues analysed. Each of them either reached impasses due to internal problems, or included features that made them unacceptable even to other phlogistians. The expositions and analyses of these theories are given in terms of details that were in the literature at the time or otherwise potentially understandable by the participants given contemporary practice. Some relevant methodological aspects of the history of science are discussed, and the secondary literature is briefly surveyed. The second paper deals with the contemporary development of the new chemistry, and with theory comparison and theory choice in the same period.

Arguing About Science is an outstanding, engaging introduction to the essential topics in philosophy of science, edited by two leading experts in the field. This exciting and innovative anthology contains a selection of classic and contemporary readings that examine a broad range of issues, from classic problems such as scientific reasoning; causation; and scientific realism, to more recent topics such as science and race; forensic science; and the scientific status of medicine. The editors bring together some of the most influential contributions of famous philosophers in the field, including John Stuart Mill and Karl Popper, as well as more recent extracts from philosophers and scientists such as Ian Hacking, Stephen Jay Gould, Bas van Fraassen, Nancy Cartwright, and John Worrall. The anthology is organised into nine clear sections: science, non science and pseudo-science race, gender and science scientific reasoning scientific explanation laws and causation science and medicine probability and forensic science risk, uncertainty and science policy scientific realism and anti-realism. The articles chosen are clear, interesting, and free from unnecessary jargon. The editors provide lucid introductions to each section in which they provide an overview of the debate, as well as suggestions for further reading.

How do we refer to chemical substances, and in particular to chemical elements? This question relates to many philosophical questions, including whether or not theories are incommensurable, the extent to which past theories are later discarded, and issues about scientific realism. This chapter considers the first explicit reference to types of colorless air in late-eighteenth-century chemical practice. Reference to a gas by one chemist was generally intended to give others epistemological, methodological, and practical access to the gas. This chapter proposes a causal-descriptive theory of reference for chemical substances. Implications for debates about incommensurability and realism are also briefly noted.

This paper investigates the formation and propagation of wavefunction `branches' through the process of entanglement with the environment. While this process is a consequence of unitary dynamics, and hence significant to many if not all approaches to quantum theory, it plays a central role in many recent articulations of the Everett or `many worlds' interpretation. A highly idealized model of a locally interacting system and environment is described, and investigated in several situations in which branching occurs, including those involving Bell inequality violating correlations; we illustrate how any non-locality is compatible with the locality of the dynamics. Although branching is particularly important for many worlds quantum theory, we take a neutral stance here, simply tracing out the consequences of a unitary dynamics. The overall goals are to provide a simple concrete realization of the quantum physics of branch formation, and especially to emphasise the compatibility of branching with relativity; the paper is intended to illuminate matters both for foundational work, and for the application of quantum theory to non-isolated systems.

Complexity is heterogenous, involving nonlinearity, self-organisation, diversity, adaptive behaviour, among other things. It is therefore obviously worth asking whether purported measures of complexity measure aggregate phenomena, or individual aspects of complexity and if so which. This paper uses a recently developed rigorous framework for understanding complexity to answer this question about measurement. The approach is two-fold: find measures of individual aspects of complexity on the one hand, and explain measures of complexity on the other. We illustrate the conceptual framework of complexity science and how it links the foundations to the practised science with examples from different scientific fields and of various aspects of complexity. Furthermore, we analyse a selection of purported measures of complexity that have found wide application and explain why and how they measure aspects of complexity. This work gives the reader a tool to take any existing measure of complexity and analyse it, and to take any feature of complexity and find the right measure for it.

"The doctrine of materialism is one of the perennial and most controversial ideas in the arts and sciences. Throughout history it has aroused strong passions, and in the Sixteenth and Twentieth centuries was a doctrine over which people were persecuted and killed. Yet it has been equally aligned with empirical, enlightened and tolerant thinking. This book explores the fascinating and important philosophy of materialism in an engaging and thought-provoking way. Opening with an overview of the ideas of some of the most important materialists, including Lucretius, Epicurus, Hobbes and Hume up to Darwin and Marx, Brown and Ladyman show how materialism's origins were twofold: it was an early form of scientific explanation but also an intellectual outlook, or belief-system, about the world in general. They then explain how materialism's beginnings as imaginative vision of the true nature of things faced a major challenge from modern physics, in the form of quantum theory and the general theory of relativity. This posed major questions for materialism: how could it be reconciled with unobservable entities and new discoveries about the nature of space and time? As the authors show, out of this challenge materialism did not die but re-emerged - as the new doctrine of physicalism. Drawing on colourful examples throughout - from modern physics, the nature of the mind, and atheism - the authors argue that whilst materialism may not have all the answers, its humanism and staunch belief in observation, evidence and experiment remains our best hope in a fragmented and hyper-specialised world"--