The following is a continuation of my summary of, much of it quotes and paraphrases from, Chapter 8 of A Metaphysics for Freedom by Helen Steward.
Often said about top-down causation is that if such a thing existed, it would have to involve suspension of, or interference with, operative laws at the lower level. But how does the apparent commitment to law violation arise from the assumption that certain psychological states and events can cause the cells and molecules in a bird’s body to move? Why would physical laws be such that do not allow for any variation according to their setting? Is it that laws of physics completely dictate the movements of all physical things? What if they only constrain the movements without dictating every detail? A free falling tennis ball will obey Newton’s laws of gravity and the laws predict its travel without interference, but interference is possible. There is no scientific reason to endorse the claim that physical laws completely dictate movement. There is only the grip of a mesmerising world view.
John Searle has argued there is no room for free will because neurophysiology settles everything. On the other hand Roger Sperry defends downward causation on the grounds of emergent properties. We cannot understand the movement of a small part of a wheel apart from understanding the movement of the whole wheel.
“Our standard model for causation involves one object impacting on another and thereby producing a change in it, usually a change in properties that relates to its motion (though perhaps not only those.) The wheel certainly does not impact on the molecule in this way, but must that be the only kind of causal interaction we can envisage? Might there be types of causal affecting that obtain only in the special case where one object is part of another?” (p.235).
“The key to to this puzzle about top-down causation, I think, is the phenomenon of coincidence. For in general the ‘basal conditions’ from which complex entities may be said to ‘emerge’ tend to be complex conditions, which require for their generation that a great many quite separate things occur together or else in some precise order, or (more usually) both” (p. 236).
“That molecules are in this special kind of arrangement, that they are ordered in the necessary way, is a fact that is to be causally explained by appeal to someone’s plans and designs: a wheel was wanted and so a wheel got made. Without this part of the causal story, it would just be an enormous and totally inexplicable coincidence that the universe had managed to throw up molecules arranged wheelwise” (p. 237).
“Causation is about how things come to be. Where certain things require for their coming to be that complex synchronous arrangements to exist has to be part of the causal story, part of the relevant metaphysics of causation and not just part of what is required to satisfy the intellectual curiosity of the investigator” (p. 239).
“The question is how on earth a whole person or animal could manage to have effects on its own parts in such a way that causation does not simply reduce to the causation of parts on parts? It is of course not possible for me to give a full account here of what the cause of human action actually involves, for that is the scientific question to which there will have to be scientific answers” (p. 243).
An animal could affect things without its role collapsing into the role played by the various lower-level entities out of the activities from which its own doings emerge. It is essential to avoid thinking of the animals input as something prior to whatever neural processes initiate and then monitor and control the relevant bodily movement or change.
“In more complex animals [ ] it seems the need to respond swiftly to the ever-changing demands of an unpredictable environment has made it imperative that the integration of subsystems be organized overall by a top-level system that differs from the other systems that operate in it in a special way. The important new feature of the top-down system is discretion [ ] as to optimize its chances of survival and success.” (p. 245)