Re: earlier points made on emergence, I have something that I've only recently come to formulate.
The back and forth on this thread, it appears to me, is over the possibility that an assemblage might amount to more than the sum of its parts versus the impossibility of this phenomenon. In the latter's view, the appearance of emergence (this perspective might even say "illusion") merely derives from our current inability to properly assess and understand all the working parts; but, provided that we could achieve such a complete understanding, all systems could be successfully reduced to their individual components.
I believe that the latter argument derives from a misinterpretation or misunderstanding of what exactly emergence entails. Emergence isn't some quasi-mystical argument for positing forces that exceed us or for paving a route to some ideological theory of communal society (i.e. there are no individuals, only aggregates, etc.). It is a theory that allows us to conceptualize and critique real social and natural processes; and we can see it at work all around us.
If all systems can be reduced to their individual components, then we very abruptly lose the ability to even apprehend interactive networks at higher/larger levels. Likewise, if we only take into consideration elements and interactions on the macro scale, we lose the partially constitutive presence of the pieces internal to these larger entities. I think emergence theory can become readily available to us by taking the example of the human body.
A human body is made up of cells. These cells engage in their own interactions and processes, and carry out functions very immediate to their scale. Without these cells, we would not have a human body; the cells comprise blood, skin, organs, tissue, muscles, bone, etc. They are fundamental to the composition of a human body.
Prior to emergence and other theories that fall under the category of complexity (which only began to appear in the last 150 years or so), the basis of human action, cognition, being, etc. had to be attributed to some kind of essential power or source within the human - Descartes's pineal gland, Kant's transcendental subjectivity, Bergsonian vitalism, or (prior to all) simply the infusion of the creative power of God. Beyond cells, tissue, bone and blood, there had to be a wellspring of being that bestowed consciousness and subjectivity onto the human.
Today, in the sciences and in theories of emergence, such essences are obsolete. Instead of positing a sacred or mystical force that regulates and transcends the bodily, we can theorize how complex systems such as consciousness arise from the basic material systems of the human body. This is how emergence theory can suggest that interactive components amount to "more than the sum of the parts." The human body, despite being comprised of cells, cannot be reduced to its cells because cells do not participate in market transactions; cells do not play sports or music; cells do not build houses or cities. The networks and processes that occur between what we call human agents cannot be reduced to the workings of cells.
In the same sense, the evolution of social/cultural fields - psychology, philosophy, engineering, physics, biology, etc. - cannot be reduced to human agents. As is the case with cells, we can posit that to take away the humans would be to take away any development whatsoever; but this is not to say that these developments are completely reducible to humans. Such complex phenomena can only be conceptualized via larger aggregates of human interaction and participation, which is why we organize humans into schools, institutions, private corporations, political bodies, etc.
Processes and functions take place on every level; cells carry oxygen through the body, corporations and private businesses feed money through a society, individual people use this money to trade with other people, thereby giving themselves energy, ensuring that they keep breathing and thus allowing their red blood cells to continue carrying oxygen. Just as it makes no sense to reduce a human to the cells that carry oxygen and fight off antigens (a reduction that precludes any interaction at higher levels), it makes no sense to reduce cultural development and change to human agents - cultural change takes place within an environment that includes people as well as machines, trees, animals, technologies, thunderstorms, etc.
Emergence does not insist upon science-fictional forces or mystical powers that subsist on their own, regardless of material environment. It attempts to provide a philosophical and scientific means of observing how different networks of symbiotic behavior take place on different levels of complexity, and offers ways to conceptualize these behaviors that adhere to the conditions of that level's environment. Emergence would never claim, absolutely, that technological development could have taken place without human intervention (although it may continue without human intervention, at some point); but this does not mean that technology can be understood purely as the intentional and purposeful cooperation between human agents. Neither of these positions makes sense. Rather, emergence allows us to perceive that technological developments such as - for instance - space travel or cybernetics takes place on a plane of complexity significantly beyond that of red blood cells.
EDIT: I have a new post on my SF blog, on the movie Snowpiercer.
