We may not be able to finitely prespecify all the possible systems that constitute an autonomous agent, but we can recognize one when we see it.

The trouble is, it appears to be impossible to finitely prespecify a set of statements about sense data whose truth is logically equivalent to statements about chairs.

I will claim that we cannot finitely prespecify the configuration space of a biosphere, hence, we cannot finitely prespecify the initial and boundary conditions of a biosphere.

Again, we can give several suYcient conditions, but apparently we cannot finitely prespecify a set of necessary and suYcient conditions that would allow us to prespecify all the possible patterns of construction, constraint, and organization of physical processes and matter flows that would constitute an autonomous agent.