Life as a physical process

The text argues that defining life only from examples on Earth makes the question too narrow. Instead, it proposes understanding life as a physical process that generates systems that are statistically unlikely to assemble and persist on their own, which would make it possible to look for life in unexpected places in the universe.

From “Life as No One Knows It”, the author summarizes Assembly Theory as a way of thinking about objects by assembly index and copy number. Objects with a high assembly index and high copy number would indicate a selection process underway, because they would not arise only randomly. In this view, life stops being binary and becomes a degree of aliveness linked to what an object produces in relation to what it consumes, with a comparison between this idea and human agency and a hypothesis that AIs could also count as alive.

Reading notes

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• The definition of life still has no consensus, and the text contrasts explanations based on entropy and on emergent properties of chemicals.
• The author says that looking only at bacteria, zebrafish, and fruit flies keeps the discussion tied to the only form of life we know on Earth.
• The more useful question, according to the text, is to seek a definition of life as a precise physical phenomenon, without depending on earthly characteristics.
• The formulation presented summarizes life as a physical process that produces systems statistically unlikely to assemble and persist by themselves.
• Assembly Theory is described as a proposal that assigns to each object an assembly index and a copy number.
• The assembly index is explained as the minimum number of steps to assemble an object from available building blocks, as in an analogy with Lego pieces.
• The copy number indicates how many copies of an object exist in the universe.
• The text says that objects with a high assembly index suggest a history of selection, because they would not have arisen by chance.
• In the passage on applications, the author notes that the theory seems to work well at the chemical level, with molecules formed from atoms.
• The text admits uncertainty about how to calculate assembly index for things like stars or kidneys.
• From statistical improbability, life is presented as the study of patterns and as a creative force that produces artifacts that would not assemble spontaneously.
• The text proposes that life should not be treated as something binary, but as a degree of aliveness linked to the effect of an object on the environment.
• The measure of this degree appears in the difference between the complexity of the outputs and that of the inputs consumed.
• The author brings this reading close to the idea of agency, saying that people with high agency shape the environment, while those with low agency are shaped by it.
• At the end, the text suggests that AIs may also be considered alive in this sense, because they are complex objects in multiple copies that help produce other statistically unlikely objects.