[Paper Review] The "Hard Problem" of Life

Sara Imari Walker, Paul Davies|arXiv (Cornell University)|Jun 23, 2016

Misinformation and Its Impacts4 citations

TL;DR

The paper proposes that the 'hard problem of life' lies in understanding how information exerts causal influence in biological systems—specifically, how macroscopic, information-encoded states govern dynamics in ways not reducible to known physical laws. It argues that life's distinctiveness stems from information's causal role, analogous to qualia in consciousness, and that resolving this requires new physical principles beyond current frameworks.

ABSTRACT

Chalmer's famously identified pinpointing an explanation for our subjective experience as the "hard problem of consciousness". He argued that subjective experience constitutes a "hard problem" in the sense that its explanation will ultimately require new physical laws or principles. Here, we propose a corresponding "hard problem of life" as the problem of how `information' can affect the world. In this essay we motivate both why the problem of information as a causal agent is central to explaining life, and why it is hard - that is, why we suspect that a full resolution of the hard problem of life will, similar to as has been proposed for the hard problem of consciousness, ultimately not be reducible to known physical principles.

Motivation & Objective

• To identify a core, irreducible feature of life that resists explanation via known physical and chemical principles, analogous to the 'hard problem of consciousness'.
• To argue that the central challenge in understanding life is not its origin per se, but how information causally structures biological systems.
• To propose that the causal efficacy of information—encoded in coarse-grained macrostates—constitutes a fundamental departure from standard physics.
• To motivate the need for new physical laws that account for information-driven causation in living systems, especially in astrobiology and origins-of-life research.
• To unify biological organization across scales (molecular to societal) by identifying information as a universal, hierarchical principle of life.

Proposed method

• Analyzes the distinction between 'easy problems' of life (e.g., replication, metabolism) and the 'hard problem'—information's causal role.
• Draws analogy between the hard problem of consciousness (qualia) and the hard problem of life (information causality), both resisting reductionist explanation.
• Applies concepts from information theory (Shannon and Boltzmann entropy) and thermodynamics to show that information is physical but not fully captured by standard physics.
• Examines coarse-graining as a mechanism for defining biologically relevant macrovariables, questioning whether these are objective or subjective.
• Proposes that causal macrostates emerge from information-encoding dynamics, suggesting that such states are not just descriptors but active drivers of system behavior.
• Argues for a paradigm shift in physics to include information as a fundamental causal agent, akin to energy or momentum, in biological systems.

Experimental results

Research questions

• RQ1 What distinguishes life from non-living physical systems in terms of causal dynamics, and why is this not reducible to known physics?
• RQ2 Why does the causal role of information in biological systems resist explanation via standard physical laws, even when information is physically instantiated?
• RQ3 How can we define universal features of life that transcend chemistry and apply across biological hierarchies (e.g., cells, societies)?
• RQ4 To what extent is the causal efficacy of information in living systems intrinsic to the dynamics, rather than a mere phenomenological description?
• RQ5 What new physical principles might be required to account for information-driven causation in life, especially in the context of astrobiology and origins-of-life research?

Key findings

• The hard problem of life is not the origin of replication or metabolism, but the causal influence of information in shaping biological dynamics.
• Information is physical (per Landauer), but its role as a causal agent in living systems cannot be reduced to known physical principles.
• Biological systems implement state-dependent dynamics by attributing causal efficacy to information encoded in macrostates, a feature absent in non-living systems.
• The distinction between objective and subjective coarse-graining remains unresolved, suggesting that macrostates may be fundamental to biological organization.
• Life’s hierarchical organization—from cells to societies—can be unified through the principle of information as a causal force, suggesting universality across scales.
• A new physical theory may be required to explain how information causally structures living systems, paralleling the revolutionary shifts brought by relativity and quantum mechanics.