The boundary layer between living and living intentionally, however, is one which he chose not to explore, perhaps because he estimated rightly that the science of his time would not accept the effort.
A system achieves living through a certain combination of ingredients and systems sufficient to obscure authorship and invite a snuggly place for life force to give and receive sensation. Living systems, in turn, develop from the sensate but uninspired efforts of the cell, to the organ, organism, organization, and the Great Organa - the species as an organism. At some point in this ladder, the composite of molecules, charges, and attention achieves aware will and the ability to select an intention and execute it.
One of the aspects of Miller's work is the process of information relay and assimilation. Piaget and his heirs have been interested in how the process of information assimilation develops in children; interestingly, the very young seems to learn words before he can speak quite as well as one who already speaks can learn them. Some evidence exists for non-comprehending retention of force and meaning in records of experience even in the prenatal zone; so there is something in the assimilation of experience which whether it is understanding or not occurs before myelin sheathing is set up fully. How this can be is a mystery of you believe in neurology as the sole seat of knowing.
The transition in systems to intentionality (if that is the key differentiative factor) from pre-intentionality may have a critical point that precipitates it something on these lines:: when assimilation of data is sufficient to transcend the boundary between "within" and "without", to sort out the apparent existence of an external world and exercise judgment "in it" (or more likely in a created mockup of it), intentionality can occur.
This is a low level transition from some perspectives and yet seems more than some people are capable of when they are badly battered in the world. Forces greater than can be handled in the mind tend to glue one into it. In the other direction, outgrowing all such forces tends to do away with the distinction between within and without as one becomes all one sees and places intention in any part of it.
It is between these two extremes that we have organisms finding things to do to the external world and generating intentions into it from within.