Causation as Constraints in Causal Set Theory

Phil Dowe

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.

Philipp G. Frank, Robert S. Cohen

Rafael Chaves, Christian Majenz, David Gross

It is a relatively new insight of classical statistics that empirical data can contain information about causation rather than mere correlation. First algorithms have been proposed that are capable of testing whether a presumed causal relationship is compatible with an observed distribution. However, no systematic method is known for treating such problems in a way that generalizes to quantum systems. Here, we describe a general algorithm for computing information–theoretic constraints on the correlations that can arise from a given causal structure, where we allow for quantum systems as well as classical random variables. The general technique is applied to two relevant cases: first, we show that the principle of information causality appears naturally in our framework and go on to generalize and strengthen it. Second, we derive bounds on the correlations that can occur in a networked architecture, where a set of few-body quantum systems is distributed among some parties. Empirical data can contain information about causation rather than mere correlation. Here Chaves et al. present an algorithm for computing constraints on the correlations arising from a given quantum causal structure, and apply this framework to the information causality principle and networked architectures.

Federico Laudisa

Ryuhei ISHIBASHI

We propose that causation does not exist in the physical worldbut explanationdoes. Our framework distinguishes two structures often conated: derivation (the-orems follow from axioms) and causation (events produce other events). Physicsretains the former while eliminating the latter. Beginning from constraint axiomsempirically discovered structures that cannot themselves be derivedwe show thatapparent causal claims become theorems: synchronization, phase transitions, andmeasurement outcomes are derivable from constraint geometry, not produced bycausal mechanisms. The quantum measurement problem dissolves because col-lapse presupposes causation; what remains is constraint satisfaction. Entanglementis correlation constraint, not action at a distance. Spacetime emerges as a perspec-tival feature of embedding within atemporal constraint structure. We situate thisframework relative to Adlam's constraint-based laws, Rovelli's relational quantummechanics, and ontic structural realism. The methodological principle is: axiomscannot be causally explained (this would require prior causes), but theorems can bederived from them. Explanation terminates not in deeper causes but in empiricallydiscovered constraint structures.