Ellis’s Strong Emergence and Top-Down Causation

Mathematical physicist George Ellis approaches consciousness by combining non-reductionist strong emergence and top-down causation in the context of “possibility spaces” (Ellis, 2017a). While he calls consciousness “the biggest unsolved problem in science,” he sees the larger vision that consciousness transforms the nature of existence itself such that existence is quite different than it might have been had there been only nonconscious matter (Ellis, 2006).

Ellis begins with four kinds of entities, or “Worlds,” whose existence requires explanation: matter and forces, consciousness, physical and biological possibilities, and mathematical reality. An adequate explanation of what exists, he says, must encompass all four kinds of entities, in two forms: generic forms of the kinds of entities that might exist, and specific instantiations of some of these possibilities that actually occur or have occurred in the real universe. The first are possibilities, and the second are actualizations of those possibilities (Ellis, 2015).

“Possibility spaces,” then, show what is and what is not possible for entities of whatever kind we are discussing. For example, the possibility space for classical physics is all possible states of the system; for quantum physics, the state spaces for the system wave function are Hilbert spaces.

For consciousness, possibility spaces include separate subspaces for all possible thoughts, all possible qualia, all possible emotions—each with its own character. Ellis says, “The rationale is always the same: if these aspects of consciousness occur, then it is possible that they occur; and that possibility was there long before they ever occurred, and so is an abstract feature of the universe. The physical existence of brains enables their potential existence to be actualized” (Ellis, 2015).

Strong Emergence and Top-Down Causation

Ellis embeds his theory of consciousness in the presence and power of strong emergence, where properties of a system are impossible to predict in terms of the properties of its constituents, even in principle; and of top-down causation, where higher hierarchical levels exert causal force on lower levels, even though the higher levels are comprised only of the lower levels. Strong emergence, according to Ellis, works throughout the physical world, particularly in biology where the whole is more than just the sum of its parts (Ellis, 2017b, 2019).

He explains that “emergence is possible because downward causation takes place right down to the lower physical levels, hence, arguments from the alleged causal completeness of physics and supervenience are wrong. Lower levels, including the underlying physical levels, are conscripted to higher level purposes; the higher levels are thereby causally effective, so strong emergence occurs. No violation of physical laws is implied. The key point is that outcomes of universally applicable generic physical laws depend on the context when applied in specific real world biological situations … including the brain” (Ellis, 2019).

Continuing to focus on emergence and downward causation, Ellis “considers how a classification of causal effects as comprising efficient, formal, material, and final causation can provide a useful understanding of how emergence takes place in biology and technology, with formal, material, and final causation all including cases of downward causation; they each occur in both synchronic and diachronic forms.” Taken together, he says, the four causal effects “underlie why all emergent levels in the hierarchy of emergence have causal powers (which is Noble's principle of biological relativity) and so why causal closure only occurs when the upward and downward interactions between all emergent levels are taken into account, contra to claims that some underlying physics level is by itself causality complete” A key feature, Ellis adds, is that “stochasticity at the molecular level plays an important role in enabling agency to emerge, underlying the possibility of final causation occurring in these contexts” (Ellis, 2023).

Critiques of Reductionism and Open Questions

Ellis's two points here, if veridical and representing reality, would have extraordinary impact on theories of consciousness, and the two bear repeating: (i) emergence has causal powers at all levels in biology, and (ii) top-down causation as well as bottom-up causation is necessary for causal closure. At once, almost every Materialism Theory—maybe every Materialism Theory (more than 90 at last count)—would be shown insufficient to explain consciousness (even if one or more were still necessary to do so).

Ellis highlights questions that he claims reductionists cannot answer: “Reductionists cannot answer why strong emergence (unitary, branching, and logical) is possible, and in particular why abstract entities such as thoughts and social agreements can have causal powers. The reason why they cannot answer these questions is that they do not take into account the prevalence of downward causation in the world, which in fact occurs in physics, biology, the mind, and society” (Ellis, 2017b, 2019).

David Chalmers distinguishes strong downward causation from weak downward causation. “With strong downward causation, the causal impact of a high-level phenomenon on low-level processes is not deducible even in principle from initial conditions and low-level laws. With weak downward causation, the causal impact of the high-level phenomenon is deducible in principle, but is nevertheless unexpected. As with strong and weak emergence, both strong and weak downward causation are interesting in their own right. But strong downward causation would have more radical consequences for our understanding of nature.” However, Chalmers concludes, “I do not know whether there is any strong downward causation, but it seems to me that if there is any strong downward causation, quantum mechanics is the most likely locus for it … The question remains wide open, however, as to whether or not strong downward causation exists” (Chalmers, 2008).