One of the take-home messages of A World from Dust is that concepts like causation and function can look different at different "levels" of the world. I was listening to Walter Isaacson's The Innovators: How a Group of Inventors, Hackers, Geniuses and Geeks Created the Digital Revolution this morning when a historical analogy occurred to me.
You may have heard that the Internet was created as a radically decentralized system so that it could withstand a nuclear attack. You have also have heard the scientists who invented the Internet loudly proclaiming that it had no such purpose. Which purpose was it? Both are true, and Isaacson does a good job of showing how.
The engineers and academics working on the nascent Internet technology were building a new way to pass around information. They had no reason to anticipate its military use or purpose. Yet the higher up the chain of command you go, the more you find the military purpose layered on top of the basic communications purpose. The people getting the money from Congress justified its expense with the military purpose that it could withstand a major, disruptive attack. The scientists didn't need that purpose at their "layer" of knowledge; the politicians required it at theirs.
In the same way, a process that is for one purpose locally may serve an additional purpose globally. A chemical process may serve and shape a biological function. Random gene flow and change may interact with a chemically ordered environment to produce a predictable change and even increase in complexity. In fact, a random process can gain a function at a higher level. The genes and elements may not "know" that the network they're building has a biological purpose, but that in no way negates the biological purpose. (For more on how this might happen, read Terrence Deacon's Incomplete Nature.)
In A World from Dust I focus on the "politicians" of the process, the legislative branch of chemical law-makers that we call the periodic table. These chemical rules result in predictable patterns emerging from random flow. You can stand close to the waterfall to see the random flow, or step back to see that it inexorably flows down and looks similar from moment to moment. It's all a matter of the width of your scope and your point of focus on the chain of command.