Is Life Defined by Agency?

The concept of 'biological agency'—the idea that life formulates its own objectives and acts to achieve them—challenges our fundamental understanding of existence. Yet, does this concept hold scientific merit? In 1993, a research team led by planetary scientist Carl Sagan tentatively concluded that life existed on Earth. This might seem like an obvious deduction. However, the researchers relied solely on data from the Galileo spacecraft, which had flown past the planet three years prior during its journey to Jupiter. The transformative power of life is so profound that its presence can be detected through the light and radio waves the planet emits or reflects into space. Scientists now scan the cosmos for these specific signatures in distant star systems.

Life leaves a distinct mark, yet there is no scientific consensus regarding what makes living entities fundamentally different from inorganic substances such as rocks, gases, and oceans found on dead worlds. Many scientists point to properties like replication or metabolism. Others describe life in abstract terms, noting that living systems exist in a state of thermodynamic disequilibrium with their surroundings. However, some propose a different answer. Living organisms are distinct because they act for reasons.

Merely stating that life is an organized, nonequilibrium state characterized by constant energy flux is insufficient. This description also applies to hurricanes. Hurricanes simply exist. Only living entities possess goals: to find food, to reproduce, to survive, or even to seek pleasure. This is not a uniquely human trait, as pet owners well know. One way to express this distinction is to say that living organisms possess 'agency.' This is a highly contested term. Some biologists reject it entirely for any organism other than humans, arguing that humans are the only species capable of conscious deliberation. Others argue that agency is a fundamental attribute of all life. Because there is no agreed-upon definition, the term can mean various things. Nevertheless, the debate touches on core issues in biology and philosophy, specifically teleology, the apparent purposiveness of life. Introducing agency into biology risks inviting concepts like design, vitalism, or cosmic meaning. Alternatively, it may simply acknowledge a special state of matter.

To me, the notion of agency aligns with our intuitive sense of what makes life special. Living things are not mere machines pushed around by environmental circumstances. I suspect that the aversion to agency reflects a discomfort with viewing life as something more than a genetic program. However, the concept carries danger. It could derail the mechanistic explanations that drive scientific progress. My goal is not to praise or bury agency, but to explore its scientific productivity.

Stating that living things are goal-directed is not controversial. Evolutionary theorist Ernst Mayr and molecular biology pioneer Jacques Monod both acknowledged this. Whether observing a bird building a nest or a white blood cell pursuing a bacterium, we cannot watch life at work without assuming these entities are attempting to accomplish something. The debate centers on what this means. In one view, apparent goal-directedness is merely the result of genetic instructions executing themselves. Organisms are automata directed by genes, with natural selection favoring variants that promote specific behaviors. In this mechanistic view, agency is simply automated routines refined over generations.

Is this the entirety of life? It is unclear if all behavior can be attributed to specific genes. Consider a hare fleeing a fox. Genes contribute to the neural networks enabling escape behaviors, but do genes determine the decision to dart left or right, or to stand and fight? Genetics may impose biases, such as risk aversion, but organisms integrate contextual information on the fly, including learned experiences. In this view, agency is the capacity to set proximal goals—not abstract questions like 'Shall I reproduce?' but immediate questions like 'What action should I take now?'—and then act upon the environment to achieve them.

Neuroscientist Kevin Mitchell of Trinity College Dublin describes agency as the capacity of an entity to act in the world for its own reasons. In his 2023 book, Free Agents: How Evolution Gave Us Free Will, he argues this capacity developed through evolution. Mitchell views all living organisms as causal entities, not merely vehicles steered by genetic prompts. He warns against rigid definitions that force an all-or-nothing classification. Instead, he suggests that a holistic, ecologically contextualized view of behavior inevitably investigates agency.

Samir Okasha, a philosopher of biology at the University of Bristol, is hesitant to use this framework. He distinguishes between organisms being real agents and merely acting as if they are. He argues that agency often seems like a fancy synonym for phenotypic plasticity, the ability to show different responses to stimuli. Without the ability to self-consciously reflect on options, does this rise to true agency? James DiFrisco of the Francis Crick Institute in London agrees. He notes that agency is a psychological concept rooted in human discourse, involving intentions, beliefs, and freedom. Applying it to all life risks imputing cryptic self-awareness where it does not exist.

DiFrisco argues that the goal-directedness of organisms is a state of adaptation shaped by natural selection. To claim organisms devise their own goals is untestable and nonexplanatory, unless dealing with cognitive subjects capable of reporting mental states. In 2025, DiFrisco and Richard Gawne published a critique arguing that biological agency lacks a research program. They claim it either reiterates known biology or conjures a vague 'holistic power' resistant to mechanistic explanation, similar to the 18th-century notion of a vital force.

Biologist Sonia Sultan of Wesleyan University disagrees, arguing these critics misunderstood the proposal. She emphasizes that developmental and evolutionary agency are physical outcomes of natural processes, lacking conscious desire or intentionality. In 2022, Sultan, biologist Armin Moczek, and philosopher Denis Walsh argued that agency fills explanatory gaps left by gene-focused approaches. They define biological agency as the capacity of a system to participate in its own persistence by regulating its structures in response to conditions.

Philosopher Álvaro Moreno of the University of the Basque Country supports this, noting organisms do not just respond to environments but modify them. Even Charles Darwin recognized this, so agency does not challenge Darwinism. Historian Jessica Riskin notes that Jean-Baptiste Lamarck believed life was creative agency, contrasting with divine origin theories. Both Darwin and Lamarck placed the organism's ability to act at the center of their theories.

These choices feed back into evolution. Decisions to change diet or habitat alter selective pressures. No gene instructs an organism to eat a new plant; the organism takes initiative. This is known as 'behavioral drive,' akin to the Baldwin effect, where non-innate choices create selective pressures that eventually become genetically fixed. Excluding agency from evolution is too late.

Why use the term? Behaviors are already studied through neurology, biophysics, and ethology. DiFrisco argues that using 'agency' muddies the waters, creating circular explanations. For him, organismal decisions are convenient shorthand for multiscale mechanisms. For me, the key is that actions are governed by reasons. The hare is genuinely trying to escape, not merely appearing to. Evolution builds entities that try to do things.

The key question is what agency offers that other concepts cannot. Mitchell argues it must be 'naturalized' into a proper theory to be useful for science. Currently, no such theory exists. Challenges include determining how organisms set goals, how these are represented in neural or molecular mechanics, and whether we can measure agency. Theoretical biologist Stuart Kauffman argues that 'organizational closure' gives systems causal power, allowing them to act on their own behalf. Neuroscientist Karl Friston suggests agency arises in entities that predict outcomes and minimize error, without requiring conscious awareness.

While abstract, these ideas may unite with biological mechanisms. It is unlikely that organisms showing more agency lack molecular pathways open to contextual influence. Understanding agency could clarify how collective goals arise, as in multicellularity, or break down, as in cancer. It might also guide the creation of artificial agents that formulate their own goals, rather than following programmed ones. Ultimately, recognizing agency may help us understand what makes life uniquely capable of shaping a planet in ways visible from space.

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