Notes on Paul Nurse’s What is Life?. Contains spoilers.
Jumping right to the end, life is summed up in three principles, that living things:
- evolve (reproduce, with heredity and variation).
- are bounded, physical entities, separate from their environment, like cells.
- are “chemical, physical, informational machines. They construct their own metabolism and use it to maintain themselves, grow and reproduce.”
If you find something that ticks all three boxes, it is alive.
That second principle “invokes the physicality of life, which excludes computer programs and cultural entities from being life forms, even though they can appear to evolve.” I’d query why why software is excluded: is that based on what we know today, or an in principle position?
It’s a short book (~212 pages), physically lovely in hardback (not much bigger than your hand), and feels like the author is talking to you, rather than lecturing. Recommended.
Still, if you prefer watching to reading, there’s a Royal Institute lecture on YouTube.