[dekhn]

the operational definition agreed on in mainstream science is that to be living, you have to do regulated metabolism. This definition mainly exists to distinguish viruses from cells; I'm sure there are even cells which don't metabolize, but those are exceptional cases in which the ability to metabolize was lost in a parasitic situation.

Spiegelman's monster isn't alive under any common definition of alive, but it has fascinating properties nonetheless and appears to be an attractor in the RNA sequence space, which is quite interesting on its own.