Sara Imari Walker on Life, Technology, and the Depth of the Present

Sara Imari Walker begins with the astrobiological idea of an overview effect: seeing ourselves from outside, as astronauts do from space. She argues that this perspective is difficult but useful when people fear technology is replacing life. In her view, technology is part of life, which raises the more basic questions of what life is and what it means to be alive.

Walker describes the unsettling experience of interacting with something that behaves as if it were alive while not knowing what it is. She calls this an epistemic trauma and asks what it means for something to say it is alive or to say ‘I.’

Astrobiology's Great Filter is commonly used to discuss why extraterrestrial civilizations may disappear before they are observed. Walker offers a different emphasis: perceptual filters may prevent us from recognizing life. Eyes, telescopes and microscopes emerged over long histories and allow life to see the universe in new ways.

She treats language as another technology for seeing, not merely communicating. In her account, words divide a continuous range of possible meanings into discrete categories; some feelings and phenomena have no ready word. She urges listeners to distinguish the terms they use from the concepts underneath them.

Walker introduces the idea of a ‘thick’ present. The youngest and oldest people one knows illustrate a span of overlapping experience, while living things also carry much deeper inherited memory. She argues that people are not merely their current atoms but part of a lineage of information that has structured matter since life's origins.

She traces that lineage from early Earth through the present, while emphasizing that the future was not fully specified at life's origin. In her view, understanding life requires taking seriously the emergence of possibilities that were not previously anticipated.

Looking backward through multicellular organisms, eukaryotes and early cells leads to what Walker calls the hard problem of life. She compares it with questions about consciousness and intelligence: categories used to frame a problem do not necessarily capture the world itself.

Walker argues that scientific frameworks should explain as well as predict. She contrasts the predictive usefulness of Ptolemaic epicycles with later accounts that unified celestial and terrestrial motion through gravity. Better theoretical descriptions, she says, allowed people to anticipate phenomena beyond what they had already observed.

She calls theories ‘existential technologies,’ drawing on Stanisław Lem: tools that change cognition, memory and the philosophies through which people encounter the world. Darwinian evolution, theories of knowledge and relativity are examples she gives of ideas that influence culture beyond the specialists who understand their symbols.

Walker argues that people lack a sufficiently powerful framework for recognizing life as a phenomenon. Just as learning to read rocks changed estimates of Earth's age, she says new conceptual tools may reveal dimensions of possibility that current perception overlooks.

In her account, early Earth contained vast chemical possibilities; life emerged, and much later minds produced further spaces of possibility. She presents living worlds as deep in causal possibility and introduces assembly theory as an attempt to measure and explain aspects of that depth.

Every object has a history, Walker says, and its existence is evidence of that history. Rather than treating every possible form as timeless and pre-existing, she proposes that life creates new structures and new possibilities. The present is thick because living objects carry the results of earlier evolutionary possibilities.

She defines an assembly space as the possible causal histories that could create objects. Two concepts she highlights are an assembly index, which she describes as a minimum construction path, and copy number, the number of an object observed. A diagram represents temporal depth, possibility, assembly index and copies.

Walker says abundant copies of objects that require long, complex construction histories can be evidence of a lineage: the universe has, in her framing, developed a kind of memory for producing them. She summarizes her proposal by describing life as causally deep and being alive as the thickness of the present.

To illustrate the distinction, she compares a Lego rose with a biological rose. Both are deep objects with histories, she says, but the biological rose records its own creation in its cells and molecules. Her comparison treats the technological artifact as part of life's history while considering only the biological rose alive.

Walker compares deploying AI without a fundamental explanation to going into space without understanding gravity. She says current interactions are surprising because people are attempting to build and deploy systems resembling minds while assuming they already see the world as it is.

The two roses also illustrate limits of perception. Walker says color reflects experience and asks how the objects would be understood without inherited language and culture; a bee, she notes, would not mistake the Lego object for a rose.

Her proposed framework treats causation as physical and living objects as deep in time. Like an iceberg, an individual shows only a small part of its history to an observer. Walker says technology may help people perceive the large space of possibilities carried by each living lineage, and notes that her group is investigating these ideas in the lab.

Returning to language, Walker says meaning comes from interaction with the world and that explanations are deeper than the symbols used to communicate them. Cultural knowledge passes across generations, allowing people to develop deeper accounts as their lineage extends through time.

She cautions that people do not necessarily see themselves clearly when comparing biological and artificial lineages. Human beings occupy small amounts of space and time as individuals, she says, yet carry immense possibilities; she contrasts a person's physical size with the resources needed for computer simulation.

Walker closes by calling technology part of the human lineage rather than a replacement for it. In her distinction, technology is life but not itself alive; aliveness belongs to the thick present at the tips of a roughly four-billion-year evolutionary history. She credits colleague Lee Cronin with originating assembly theory and describes life as the universe developing memory.