On Causality and Predictivity

TL;DR

This paper argues that causality is a misleading, metaphysical concept at the quantum gravity scale, and that abandoning microcausality can lead to more consistent theories like those involving fakeons.

Contribution

It extends skepticism about fundamental causality in quantum gravity, emphasizing the statistical nature of the arrow of time and proposing abandonment of causality as a core principle.

Findings

Causality is statistically illusory at microscopic scales.

Renouncing microcausality enables consistent quantum gravity theories like fakeons.

Causation requires entities acting without being part of nature, which is problematic.

Abstract

Certain approaches to quantum gravity, such as the one based on the concept of purely virtual particles (fakeons), sacrifice the cause-effect relation at very small scales to reconcile renormalizability with unitarity. Other developments have also urged caution regarding the idea of causality as a fundamental principle. In this paper, we examine the problem from multiple perspectives, including locality and predictivity, and extend the existing skepticism in several directions. Emphasizing the impact of unruly "disruptors", we point out that the illusory arrow of time associated with causality and predictivity is inherently statistical. This renders the cause-effect relation strained at the microscopic level. We also show that causation is a borderline concept that demands belief in entities which can act on nature without being part of it. Ultimately, not only is renouncing microcausality a reasonable price to pay for a consistent and predictive theory of quantum gravity (as is the one based on the fakeon idea), but the very notion of causality is misleading. Resting as it does on metaphysical assumptions, it should therefore be abandoned in fundamental physics.