Free-living Quotes

As I thought about this, I noted that the bacterium is just a physical system; it's just a bunch of molecules that hang together and do things to one another. So, I wondered, what characteristics are necessary for a physical system to be an autonomous agent? After thinking about this for a number of months I came up with a tentative definition. My definition is that an autonomous agent is something that can both reproduce itself and do at least one thermodynamic work cycle. It turns out that this is true of all free-living cells, excepting weird special cases. They all do work cycles, just like the bacterium spinning its flagellum as it swims up the glucose gradient. The cells in your body are busy doing work cycles all the time. (Stuart Kauffman)