This chapter focuses specifically on the notion of causation. Unless a causal interpretation can be given of quantum mechanics, there is a fundamental discontinuity between the quantum realm and everything else in the world. The quantum-theoretical dualism of waves and particles makes the same entity appear both as matter and as force. There are of course challenges to other basic ontological categories that come from quantum physics, such as to notions of continuity and identity. Both in philosophy and physics, there is a frequent assumption that causation is the provider or vehicle of determinism, via causal necessitation. The indeterminism of quantum physics leaves people with a more practical concern about causation. A feature of causation that makes predictions fallible is that causal processes are extremely sensitive to a change in context. The genuine interaction of multiple factors should therefore be seen as a symptom of causation rather than as something that needs to be analysed away by theoretical abstraction.
This chapter focuses specifically on the notion of causation. Unless a causal interpretation can be given of quantum mechanics, there is a fundamental discontinuity between the quantum realm and everything else in the world. The quantum-theoretical dualism of waves and particles makes the same entity appear both as matter and as force. There are of course challenges to other basic ontological categories that come from quantum physics, such as to notions of continuity and identity. Both in philosophy and physics, there is a frequent assumption that causation is the provider or vehicle of determinism, via causal necessitation. The indeterminism of quantum physics leaves people with a more practical concern about causation. A feature of causation that makes predictions fallible is that causal processes are extremely sensitive to a change in context. The genuine interaction of multiple factors should therefore be seen as a symptom of causation rather than as something that needs to be analysed away by theoretical abstraction.
Causalism is the traditional attitude of disowning all noncausal categories of determination, holding dogmatically that every connection in the world is causal. The entirely negative attitude taken by indeterminism and by empiricism toward the principle of causation is inconsistent with the very goal of science, which is the search for the objective forms of determination and interconnection. This chapter deals with the question concerning the range of validity of the causal principle. The notion of causal range of the laws of nature will be clarified and illustrated, by analyzing in some detail a typical physical law with which every student of electricity is familiar. Science seems to show neither an enlargement nor a progressive shrinking of the domain of validity of the causal principle. Most scientists and philosophers of science believed that quantum mechanics had given causality the death blow, by showing that quantum phenomena are inherently random, hence only statistically predictable.
Abstract Quantum mechanics is our most successful and versatile account of the basic constituents of matter, of their interaction and of their compounds. We introduce the theory via a sketch of its history and lay out its mathematical structure in some detail. Before this background we address the important and controversial question of how to interpret that structure. We contextualise our own position, which is linked to our account of ontological emergence as detailed in Chap. 2 , and which is mathematically best expressed in the Heisenberg picture of quantum dynamics. Indeterminism and irreversible processes are fundamental for our approach. We discuss the dialectics of the deterministic challenge to our position and argue that indeterminism in the form of quantum randomness has turned from a philosophical riddle to a technological resource. This claim is supported by a discussion of quantum information science, including some of its basic protocols. Towards the end of the chapter we argue that agency and quantum mechanics come as a package deal. For one, quantum mechanics describes the world as offering open possibilities for the future at a fundamental physical level, which is needed for real higher-order organisation, including agency. Of course, this does not in any way show that the actual existence of agents in our world is guaranteed. But it does show that general agency scepticism has no basis in physics. Second, we show that quantum mechanics is best understood as a theory that describes our agential interactions with nature, and not as a theory that represents nature from the point of view of an inert, detached observer.
For Kant causality is an a priori category of the understanding, a necessary condition for the possibility of any experience. Later Wittgenstein’s philosophy rejects transcendentalism. We can only speak of causes and effects if in some basic situations, or ‘language games’, we already treat some things as causes of what happens. Since the notion of cause becomes meaningful only within a language game, it is not unambiguous. Quantum causal language games presuppose the use of quantum theory. We treat the latter as Wittgenstein’s grammar of a quantum form of life’, or rule (norm), anchored in its applications — quantum phenomena as language games. Quantum correlations are often interpreted as a manifestation of the nonlocality of quantum mechanics. This is a view of quantum phenomena from the perspective of classical physics. Our contextual point of view rejects the nonlocality of quantum theory in the sense of instantaneous causal influence at a distance. But it does not admit its locality in the sense of classical causality either. We introduce the notion of quantum causality which allows us to treat quantum correlations as local, but context-dependent. Their formal cause is an entangled wave function. Any particular quantum correlation, identifiable in a context of its observation as a result of the wave function reduction, post factum can be treated as a classical causal correlation. From the point of view of the proposed contextual quantum realism, epistemology is secondary, and ontology is sensitive to context. Quantum correlations exist (are real) before application of the theory, independently of their identification (description, measurement), but have no identity, which appears only as a result of application of the theory and their identification in the context. In other words, they are real, but not pre-determined, not autonomous.
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.
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.
Abstract There is widespread agreement that quantum mechanics has something radical to teach us about causation. But opinions differ on what this is. Physicists have often taken the central lesson to be that many physical events occur spontaneously, so that a principle of causality is violated whenever an atom emits light, or a uranium nucleus decays, even though nothing that happened beforehand made this inevitable. Feynman urged philosophers to acknowledge that this implication of quantum mechanics undermines the view that causal determinism forms a precondition of scientific inquiry. But while some physicists have denied the implication, most philosophers since Reichenbach have accepted it with alacrity, and sought to develop accounts of causation equally applicable in an indeterministic or a deterministic world.