Biological Theory’s new issue, 21(3), opens with an article by Philipp Mitteroecker that discusses the notion of measurement error in biology. It questions classical realist notions of measurement and advocates an instrumentalist view that shifts the focus from an unmeasurable true value to the practical question of which biological, technical, and experimental factors influence measurement outcomes.

Mauno Vihinen introduces the concept of poikilosis, a unifying theory in biology emphasizing the inherent heterogeneity of all biological systems, maintained in a balanced state called lagom through various countermeasures. Recognizing whether a system exhibits lagom is crucial for accurate measurement, analysis, and therapeutic approaches, as deviations can lead to systemic effects and disease. Therapies aimed at restoring lagom can improve outcomes when curative treatments are unavailable.

In their two-part article (Part One, Part Two), Michael Levin and David B. Resnik review historical and contemporary debates about teleology in biology and describe groundbreaking experimental results from morphogenesis, synthetic biology, and related research on the coordination of cellular behavior through bioelectric networks. They contend that explaining these results requires biology to adopt an approach to teleology informed by mentalistic concepts, including intelligence, cognition, and intentionality. They introduce the Technological Approach to Mind Everywhere (TAME), which treats goal-directedness, information processing, learning, and problem-solving as empirically testable capacities that may occur to varying degrees in cells, tissues, organisms, and engineered systems—not only in brains.

In his Perspective article, Frederic Schiffer proposes that subjective experience is a real but biologically confined physical force that influences brain activity by biasing neural activation thresholds rather than supplying energy itself. He argues that meaning and prior experience steer the brain’s stored metabolic energy—like a control signal in a transistor—offering a speculative account of mental causation without violating energy conservation.

Rod Swenson, in his two-part article (Part One, Part Two), argues that cognition should not be treated as separate from physics: it arises within an irreversible universe whose development is driven by spontaneous symmetry breaking, rather than by perfect symmetry. He proposes the law of maximum entropy production as a “fourth law” of thermodynamics, claiming that systems select faster dissipative paths and thereby generate ordered, self-amplifying structures—from stars and convection cells to the physical foundations of agency and cognition.

The issue closes with an article by Linbo Wang, who discusses evolution in terms of thermodynamics, stressing that natural selection can be seen as a biological manifestation of the fourth law of thermodynamics. This article is published with an anonymous commentary, a commentary by Rod Swenson, and a reply by the author.