I have claimed that it is profitable to distinguish three key questions about causation. The first question, what are causal processes and interactions? , was addressed in Chapter 5. The second question, what is the connection between causes and effects? , was addressed in Chapter 7.The third question, what makes a cause different from an effect? , has not been addressed, and it is to that task that we turn in the present chapter. The question of the directionality and asymmetry of causation has long been an important ingredient in philosophical discussions of causation, although perhaps Reichenbach (1991) was the first to truly appreciate the significance of the question. It is certainly an aspect of folk intuitions. Many philosophers have held that an adequate analysis of causality should provide an explanation or account of causal asymmetry. On the other hand, it is precisely this aspect of causation that is the most common target for elimination from empirical accounts. This chapter looks at the ability of 'process' theories of causality to provide such an account, granting certain constraints. The major constraint, or premise, in the following analysis is the assumption that quantum mechanics reveals the presence of backwards-in-time causation. Thus, in the first instance, the argument presented here will not convince those who hold that there can be no backwards causation. However, I derive an empirical prediction, which, if confirmed, would give those sceptical about backwards causation reason to think again. The chapter begins with an analysis of some of the formal properties of causation. This is followed by a nontechnical presentation of the famous difficulties associated with Bell phenomena in quantum mechanics, and the backwards-in-time solution to those difficulties.
I have claimed that it is profitable to distinguish three key questions about causation. The first question, what are causal processes and interactions? , was addressed in Chapter 5. The second question, what is the connection between causes and effects? , was addressed in Chapter 7.The third question, what makes a cause different from an effect? , has not been addressed, and it is to that task that we turn in the present chapter. The question of the directionality and asymmetry of causation has long been an important ingredient in philosophical discussions of causation, although perhaps Reichenbach (1991) was the first to truly appreciate the significance of the question. It is certainly an aspect of folk intuitions. Many philosophers have held that an adequate analysis of causality should provide an explanation or account of causal asymmetry. On the other hand, it is precisely this aspect of causation that is the most common target for elimination from empirical accounts. This chapter looks at the ability of 'process' theories of causality to provide such an account, granting certain constraints. The major constraint, or premise, in the following analysis is the assumption that quantum mechanics reveals the presence of backwards-in-time causation. Thus, in the first instance, the argument presented here will not convince those who hold that there can be no backwards causation. However, I derive an empirical prediction, which, if confirmed, would give those sceptical about backwards causation reason to think again. The chapter begins with an analysis of some of the formal properties of causation. This is followed by a nontechnical presentation of the famous difficulties associated with Bell phenomena in quantum mechanics, and the backwards-in-time solution to those difficulties.
It has been claimed that quantum mechanics is a non-local theory, i.e., that the predictions of quantum mechanics are at odds with a conception of the world where all the interactions are mediated by local mechanisms. The cited reason is the violation of the Bell inequality in cases where measurements are performed on quantum systems of particles that have interacted in the past. Quantum mechanics predicts that the state of the particles in such a system are correlated, a result obtained from considering a thought-experiment often known as EPR. In this thesis, I will argue that the violation of the Bell inequality in EPR forces us to either accept that causes sometimes act both backwards and forwards in time, or give up some widely-held assumptions about causal relations or the role of causal explanations. First, I will present three principles regarding causality that I take be widely accepted. I will then present the background for the claim the quantum mechanics is a non-local theory, and discuss the implications of non-local causal influences in light of the Special Theory of Relativity. One argument against a causal explanation of the EPR-correlations will be discussed, and different models for the causal structure of EPR will be assessed. I will argue that a retrocausal model – models that include instances of retrocausation, where the direction of causation is the opposite of the direction of time – is the only viable option if we want to uphold the three principles presented in chapter 1. I will discuss the plausibility of rejecting one of these principles, and argue that at least one of the can be restricted in a way that still accounts for our commitment to it. Finally, I will assess the non-local models against the retrocausal models, and argue that a retrocausal model offers interpretational advantages over the non-local alternatives.
Philosophical analyses of causation take many forms but one major difficulty they all aim to address is that of the spatiotemporal continuity between causes and their effects. Bertrand Russell in 1913 brought the problem to its most transparent form and made it a case against the notion of causation in physics. The issue highlighted in Russell's argument is that of temporal contiguity between cause and effect. This tension arises from the imposition of a spectrum of discrete events occupying spacetime points upon a background of spacetime continuum. An immediate and natural solution is to superpose instead spatiotemporally continuous entities, or processes, on the spacetime continuum. This is indeed the process view of physical causation advocated by Wesley Salmon and Phil Dowe. This view takes the continuous trajectories of physical objects (worldlines) as the causal connection whereby causal influences in the form of conserved quantities are transported amongst events. Because of their reliance on spatiotemporal continuity, these theories have difficulty when confronted with the discontinuous processes in the quantum domain. This thesis is concerned with process theories. It has two parts. The first part introduces and criticizes these theories, which leads to my proposal of the History Conserved Quantity Theory with Transmission. The second part considers the extension of the idea of causal processes to quantum physics. I show how a probability distribution generated by the Schrodinger wavefunction can be regarded as a conserved quantity that makes the spacetime evolution of the wavefunction a quantum causal process. However, there are conceptual problems in the interpretation of the wavefunction, chiefly to do, as I shall argue, with the difference in the behaviours of probabilistic potentials between quantum and classical physics. I propose in the final chapter, the Feynman Path Integral formulation of quantum mechanics (with the Feynman histories) as an alternative approach to incorporating the probabilistic potentials in quantum physics. This account of how to introduce causal processes in quantum mechanics fares better, I claim, than the previous one in dealing with the situational aspect of quantum phenomena that requires the consideration of events at more than one time.
As the previous chapter made clear, in the present interpretation quantum mechanics gives a rather specific account of EPR-type correlations and what underlies them. In the present chapter I argue that this account is genuinely explanatory (rather than merely an idle overlay on a simple description of the observed correlations), and that this constitutes a significant advantage of the present interpretation over certain rival interpretations, on which quantum mechanics is unable to offer an adequate explanation of the observed correlations. In order to make this argument it will prove necessary to examine the character of causal explanation in theoretical science, and in particular to develop a coherent metaphysics of a kind of holistic, nonseparable, causal explanation. I take the development of such a coherent metaphysics to constitute a significant task independent of the details of the present interpretation of quantum mechanics. Quantum mechanics is a mine of metaphysical insights, and I hope here at least to have exposed a rich seam. The first task is to defend the adequacy of the present account of EPR-type correlations as at least a coherent description of what may underlie the observed correlations. I foresee three main challenges to its descriptive adequacy. The first is to claim that the account is incompatible with the relativistic requirement that there can be no direct causal connection between spacelike-separated events, and must therefore be rejected. A weaker version of this challenge is to claim that although the incompatibility just mentioned may not by itself entail rejection of the account, it does seriously undermine its claim to be genuinely explanatory.
In this chapter we introduce the postulate of causality, and derive the mathematical structure of a causal OPT. We show how the present definition of causality is equivalent to the Einsteinian one, and argue that it is the only possible notion once it is stripped from its spurious deterministic connotation. In addition, the notion of causality used here is compliant with the historical philosophical concept since David Hume, and with the idea used in common reasoning, inference, and modeling in human sciences. In brief, the present notion of causality can be stated as the requirement of no signaling from the future . This is also the only requisite for an OPT in order to satisfy the principle of no signaling without interaction . In mathematical terms in an OPT the causality postulate is equivalent to the uniqueness of the deterministic effect, which in turn is equivalent to the ability to normalize states. The notion of causality is so naturally embedded in our understanding of reality that it often remains unconsciously implicit in foundational research, even in recent axiomatizations. Causality: From Cinderella to Principle Causality has been the object of a very extensive literature encompassing hundreds of books and technical articles in a wide spectrum of disciplines, ranging from pure philosophy to economics, law, natural sciences, and obviously, physics. Also due to its involvement in such heterogeneous blend of disciplines, causality has long been a vexed notion. Perhaps the most natural connection between concepts of causality in different branches of knowledge is the one at the borderline between physics and philosophy, since the early work of Aristotle, up to the cornerstone of Renée Descartes, who broke the ground for the modern view of David Hume and Immanuel Kant, through to contemporary works on physical causation. Causality has always remained in the realm of philosophy, staying only in the background of physics, without the status of a “law” or the rank of a “principle.” Most of the time causality creeps into physical theories in the form of ad hoc assumptions based on empirical evidences, as when we discard advanced potentials in electrodynamics or when we motivate the Kramers–Kronig relations. In other cases, causality is embodied in the “interpretation” of the theory, as for the Special Relativity of Einstein.
In this dissertation, I will argue that quantum field theory can be interpreted as a description of causal interactions. I will first discuss previous theories of physical causation, and come to the conclusion that they are inapplicable in quantum field theory. As a consequence, I will start to develop a new theory of causation by first analysing the concept ‘causation’ into the most basic and widely shared intuitions, in order to find out later whether these intuitions can be reduced to physics. I will then have a closer look on the intuition that causation is a directed relation, which is commonly regarded as incompatible with the symmetries of physics. I will present a new argument to the effect that causation and quantum field theory are compatible with respect to the directionality of causation. After that, I will analyse the theoretical description of interactions in quantum field theory, and in particular group structure, locality and local conservation laws will crystallise as the central concepts that a causal interpretation might be based on. Subsequently, I will discuss and present replies to what I believe are the most relevant objections to a causal interpretation of physics, namely, Haag’s theorem, the measurement problem and entanglement. In the final chapter of this dissertation, I will conjoin the results of the previous chapters to a new theory of causation for quantum field theory. The main result will be that a causal process is a quantum field theoretical interaction, i.e., the exchange of energy from an initial to a final state via a force.
Stunning new observations and theories deepen the concept of causation. Quantum theory is one of the most striking discovery of contemporary physics, and it challenges many facets of older theories, even though it lies on many assumptions that could not be empirically experimented. In this paper, I will recall the views of Hume, Reichenbach and Einstein about the issue of causation, whereas I will focus on causal priority and temporal priority criteria in causation. Nevertheless, one task that I perform is the interpretation of these ideas by arguing them within the quantum scope. That is, trying to manifest Hume, Reichenbach and Einstein views of causation that I think as close, but I shall avoid putting straight cuts on where they differ. Direction of causal processes is dependent on the direction of time in Hume’s sense while Reichenbach explained the direction of time with irreversible processes, even if he follows the temporal priority criteria of Hume. It is stated that there is nothing faster than light by Einstein, as a result, a cause could not pass the upper limit of light. Crudely put, their thoughts all differ from the principles of quantum, because causation (causation might denote a different meaning in quantum realm) may be able to travel faster than light and the common cause principle between events is rejected in quantum realm.