ABSTRACT
In “Making Sense of Emergence”, Jaegwon Kim argues that ontological emergence does more wrong than just ‘betting against physics’; it is incoherent.1 Ontological emergence is the thesis that when aggregates of microphysical properties attain a requisite level of complexity, they generate and (perhaps) sustain emergent natural properties. What is constitutive of ontological emergence is the novel causal infl uence of emergent natural properties. One signifi cant question is how to understand the notion of novel causal infl uence. An intuitive gloss is that an emergent property provides a causal contribution that goes beyond causal contributions made by any of the lower level properties had by the system and its parts taken either in isolation or in combination. One way to capture this is to claim that the behavior of an emergent property over time is characterized by a fundamental law. A further, but natural commitment of the emergentist is that once these distinctive properties emerge from basal properties, they can exercise causal infl uence on properties at the basal levels. The emergence of these new properties is taken to affect the dynamics of properties at the basal level. (This is commonly known as ‘downward causation’.) Kim contends that such a picture cannot be sustained. Kim argues that unless emergence is given a defl ationary, epistemological interpretation, it is unworkable, because we cannot make sense of emergent properties having downward causal infl uence. He considers two varieties of emergent downward causation: synchronic refl exive downward causation and diachronic refl exive downward causation. (Refl exive because emergent properties have causal infl uence on events involving their own micro-constituents.) Kim defi nes the two varieties thus:
Synchronic refl exive downward causation. At a certain time t, a whole, W, has emergent property M, where M emerges from the following confi guration of conditions: W has a complete decomposition into parts a1, . . . , an; each ai has property Pi; and relation R holds for the sequence a1, . . . , an. For some aj, W’s having M at t causes aj to have Pj at t. (28)
Diachronic refl exive downward causation. As before, W has emergent property M at t, and aj has Pj at t. We now consider the causal effect of W’s having M at t on aj at a later time t + Δt. Suppose, then, that W’s having M at t causes aj to have Q at t + Δt. (29)
Kim thinks the synchronic refl exive variety absurd, for it seemingly involves causal circularity (modulo worries about simultaneous causation). The diachronic variety, however, escapes the circularity worries because of the time delay between the putative cause and effect. Kim surmises that diachronic refl exive downward causation is all that emergentists need. But he argues that diachronic refl exive downward causation is open to his causal exclusion argument:
. . . I earlier argued that any upward causation or same-level causation of effect M2 by cause M1 presupposes M1’s causation of M2’s lower level base, P2 (it is supposed that M2 is a higher-level property with a lower-level base; M2 may or may not be an emergent property). But if this is a case of downward emergent causation, M1 is a higherlevel property and as such it must have an emergent base, P1. Now we are faced with P1’s threat to preempt M1’s status as a cause of P2 (and hence of M2). For if causation is understood as nomological (law-based) suffi ciency, P1, as M1’s emergence base, is nomologically suffi cient for it, and M1, as P2’s cause, is nomologically suffi cient for P2. Hence P1 is nomologically suffi cient for P2 and hence qualifi es as its cause. The same conclusion follows if causation is understood in terms of counterfactuals-roughly, as a condition without which the effect would not have occurred. Moreover, it is not possible to view the situation as involving a causal chain from P1 to P2 with M1 as an intermediate causal link. The reason is that the emergence relation from P1 to M1 cannot properly be viewed as causal. This appears to make the emergent property M1 otiose and dispensable as a cause of P2; it seems that we can explain the occurrence of P2 simply in terms of P1, without invoking M1 at all. If M1 is to be retained as a cause of P2, or of M2, a positive argument has to be provided, and we have yet to see one. In my opinion, this simple argument has not so far been overcome by an effective counter-argument. (32)2
In this chapter I will provide the counterargument that Kim asks for. The purpose of this chapter is twofold: (1) to defend the internal consis-
tency of the classical emergentist position, more or less in the form as it was articulated by C. D. Broad (1925), by resisting Kim’s argument and variations on it, but also (2) to make clear the costs of embracing the classical emergentist position. These two aims correspond to the two halves of this chapter. In the fi rst half, our central concern is the possibility of diachronic downward causation by emergent properties. I begin by considering Kim’s
charge of causal circularity against synchronic refl exive downward causation. I then turn to the central issue of diachronic downward causation. I present Kim’s argument, which proceeds in two steps. The fi rst step is commonly known as the ‘downward causation argument’ and the second step the ‘causal exclusion argument’. I challenge each step in turn. This concludes the fi rst half of this chapter. In the second half of this chapter, I consider the price of embracing such a position. I approach the issue not through the usual route of what the prospects for a claim about the causal closure of the physical are, but through considering the sense in which emergent properties supervene on basal properties on the classical ontology and whether this is consistent with emergent properties having novel downward causal infl uence. I attempt to bring out a tension between having novel downward causal infl uence and supervenience by considering a putative situation where emergent properties fail to supervene. On the basis of this, I argue that supervenience in the case of emergent properties must be sui generis-grounded solely on fundamental, non-derivative emergent laws. This sets certain constraints on the explanatory potential of the classical emergentist position, since any causal infl uence by emergent properties must be consistent with patterns of co-variation between emergents and bases permitted by the fundamental emergent laws. My overarching aim is to provide a more accurate picture of the classical emergentist position and its strengths and weaknesses.
