James Ladyman

Quantum Counterfactual Communication is the recently-proposed idea of using quantum physics to send messages between two parties, without any matter/energy transfer associated with the bits sent. While this has excited massive interest, both for potential ‘unhackable’ communication, and insight into the foundations of quantum mechanics, it has been asked whether this process is essentially quantum, or could be performed classically. We examine counterfactual communication, both classical and quantum, and show that the protocols proposed so far for sending signals that don’t involve matter/energy transfer associated with the bits sent must be quantum, insofar as they require wave-particle duality.

This chapter discusses the plausibility of the criticism against the thesis that external factors causally influence cognition and that they are, consequently, partly constitutive of cognition. The discussion should not be taken as implicitly proposing that the opposite theory is true, although the works of Adams and Aizawa suggest that they are defending internalism. This can be attributed to the fact that systems are, by definition, bounded; one must make assumptions about systems in developing cognitive models. This chapter defends the position that metaphysical considerations should play no role in deciding how to model cognition. It further explains how there is no basis for a general fact of the matter about determining what is and what is not a cognitive system.

In discussion of the interpretation of quantum mechanics the terms ‘ontic’ and ‘epistemic’ are often used in the sense of pertaining to what exists, and pertaining to cognition or knowledge respectively. The terms are also often associated with the formal definitions given by Harrigan and Spekkens for the wavefunction in quantum mechanics to be ψ-ontic or ψ-epistemic in the context of the ontological models framework. The formal definitions are contradictories, so that the wavefunction can be either ψ-epistemic or ψ-ontic but not both. However, we argue, nothing about the informal ideas of epistemic and ontic interpretations rules out wavefunctions representing both reality and knowledge. The implications of the Pusey–Barrett–Rudolph theorem and many other issues may be rethought in the light of our analysis.

"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"--

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.

Social machines are systems formed by material and human elements interacting in a structured way. The use of digital platforms as mediators allows large numbers of humans to participate in such machines, which have interconnected AI and human components operating as a single system capable of highly sophisticated behavior. Under certain conditions, such systems can be understood as autonomous goal-driven agents. Many popular online platforms can be regarded as instances of this class of agent. We argue that autonomous social machines provide a new paradigm for the design of intelligent systems, marking a new phase in AI. After describing the characteristics of goal-driven social machines, we discuss the consequences of their adoption, for the practice of artificial intelligence as well as for its regulation.

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.

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.

Ladyman, Presnell, and Short proposed a model of the implementation of logical operations by physical processes in order to clarify the exact statement of Landauer's Principle, and then offered a new proof of the latter based on the construction of a thermodynamic cycle, arguing that if Landauer's Principle were false it would be possible to harness a machine that violated it to produce a violation of the second law of thermodynamics. In a recent paper in this journal, John Norton directly challenges the consistency of that proof. In the present paper we defend the proof given by Ladyman et al. against his critique. In particular, contrary to what Norton claims, we argue that the processes used in the proof cannot be used to construct a cycle that enacts erasure in a thermodynamically reversible way, and that he does not show that the processes used in the proof violate the Second Law of Thermodynamics