Mill’s account of emergence (he does not use the term himself) is the locus classicus of the British Emergentist tradition.15 Given that Mill’s treatment is utterly paradigmatic, and that my objective here is not a history of emergentism, I will concentrate on what he says.16 The crucial discussion occurs in Book III, Chapter VI, entitled ‘On the Composition of Causes’. Mill distinguishes between two models of the combined action of forces, the mechanical and the chemical.17 On the mechanical mode he says:
In this important class of cases of causation, one cause never, properly speaking, defeats or frustrates another, both have their full effect. If a physical body is propelled in two directions by two forces, one tending to drive it to the north and the other to the east, it is caused to move in a given time exactly as
13 So forces such as London forces not exerted by particle pairs are not configurational in the sense used here because they are not fundamental; they are explicable in terms of electromagnetic forces (McLaughlin 1992: 52).
14 Campbell’s (1974) label ‘downwards causation’ is generally taken to suggest the operation of independent causal powers in the manner of what I call strong emergence. His paper is ambiguous on this point, since he that ‘downwards causation’ operates ‘in complete compatibility with the physical model of causation’ (1974: 180). On the other hand he also suggests that the higher level laws (which he sees as following from natural selection) ‘determine in part the distribution of lower-level events and substances’ (1974: 180). The term ‘downwards causation’ is also sometimes used in cases where strong emergence has been ruled out entirely: Auyang’s (1998: 54f) endorsement of talk of downwards causation is immediately succeeded by the qualification that systems in which downwards causation operates have no ‘independent funds of causal power’.
15 My discussion of Mill in the present sub-section owes a great deal to McLaughlin’s elegant and careful (1992) essay.
16
References to Mill (1843) are to the text of the first edition of his System of Logic, while references to Mill (1973) are to the edition in Mill’s Collected Works including all significant changes and variations between the eight editions of the work. Quotations from this edition follow the wording of the 8th (1872) edition text. 17
In the first edition of the System of Logic he notes that the distinction is so ‘fundamental’ as to require a chapter devoted to it. In all subsequent editions the distinction is rather described as ‘radical’ (1973: 370).
far in both directions as the two forces would have separately carried it; and is left precisely where it would have arrived if it had been acted upon first by one of the two forces, and afterwards by the other. This law of nature is called, in dynamics, the principle of the Composition of Forces: and in imitation of that well-chosen expression, I shall give the name of Composition of Causes to the principle which is exemplified in all cases in which the joint effect of several causes is identical with the sum of their separate effects (1843: 428).
The model for what Mill is referring to here is Newton’s account of the composition of forces in the
Principia Mathematica. There (1934: 14)18 Newton specifies that the net effect of two mechanical forces can be shown to be represented in direction and magnitude by the diagonal vector of a parallelogram having as two of its adjacent sides vectors representing the magnitude and direction of each individual force. The notion of separating a tendency to motion19 into components is a crucial feature of Galileo’s account of projectile motion and falling bodies generally (e.g. 1914: Fourth day), and is also worked out to a different purpose in Descartes’ account of the reflection of light (1985: 156-164). For these and other thinkers the result of multiple simultaneous mechanical forces or tendencies to motion can be seen as the simple sum of the individual forces or tendencies.
Lewes (e.g. 1975: 414) called such additive forces resultants to distinguish them from the other type of force which emergentists acknowledge, which he called emergents. Mill’s version of the distinction was, as noted, between ‘mechanical’ and ‘chemical’ modes of composition, and while maintaining that most causation followed the mechanical mode, he also claimed that the principle of composition of causes did not have ‘universal validity’, that is that not all effects could be regarded as caused by the simple sum of a number of individual influences:
The chemical combination of two substances produces, as is well known, a third substance with properties different from those of either of the two substances separately, or both of them taken together. Not a trace of the properties of hydrogen or oxygen is observable in those of their compound, water. The taste of sugar of lead is not the sum of the tastes of its component elements, acetic acid and lead or its oxide; nor is the colour blue vitriol a mixture of the colours of sulphuric acid and copper (1973: 371).
Mill holds that the properties of at least some chemical compounds cannot be deduced from our knowledge of the properties of the constituents of the compound, although in a fairly typical emergentist gesture he adds that this is so ‘at least in the present state of our knowledge’ (1973: 371). I suggest that what Mill has in mind here, though, is not merely that the properties of compounds are not deducible from those of
18 The composition of forces is discussed at length in Chapter Four section (5.4) below in connection with Cartwright.
19
The term ‘force’ is either not used by these thinkers, or not used in its strict Newtonian sense, which is the reason I use the term ‘tendency to motion’ with respect to Galileo and Descartes.
their constituents, but that the laws by means of which the properties come to be instantiated are themselves not deducible either. This is to say that it is the heteropathic nature of the laws which lies behind the non- deducibility of the properties.20 Mill sums up the differences between the mechanical and chemical modes as follows:
There is, then, one mode of the mutual interference of laws of nature, in which, even when the concurrent causes annihilate each other’s effects, each exerts its full efficacy according to its own law, its unique law as a separate agent. But in the other description of cases, the agencies which are brought together cease entirely, and a totally different set of phenomena arise: as in the experiment of two liquids which, when mixed in certain proportions, instantly become, not a larger liquid, but a solid mass (1973: 373).
Although urging the distinction between mechanical and heteropathic composition, Mill is also adamant that the mechanical mode is generally operative, and regards cases of heteropathic causation as ‘exceptional’ (1973: 373). Not only that, even in cases with a heteropathic aspect the hand of mechanical composition can still apparently be discerned:
There are no objects which do not, as to some of their phenomena, obey the principle of the Composition of Causes; none that have not some laws which are rigidly fulfilled in every combination into which the objects enter. The weight of a body, for instance, is a property which it retains in all the combinations in which it is placed (1973: 373).
Heteropathic or emergent laws are to be thought of as having specific effects, and operating at definite times, or at least under definite conditions, so that the laws applicable to an entity in virtue of the laws governing the behaviour of the elements out of which it is composed when they are not configured in some way which occasions the production of a heteropathic effect continue to operate at other times. Vegetables, for example, are not to be thought of as losing their mechanical and other aspects, but rather as continuing ‘to obey mechanical and chemical laws, in so far as the operation of those laws is not counteracted by the new ones which govern them as organised beings’ (1973: 373). Not only that, it can, according to Mill, happen that the new laws may co-exist with some portion of the old, yet supersede another, and ‘may even compound the effect of those previous laws with their own’ (1973: 373), furthermore the new laws may themselves enter into simple additive compositional relationships. (1873:376). Through all these various possibilities, the hallmark of heteropathic causation in general, though, is described as follows:
... the principle of Composition of Causes [...] fails [...] where the concurrence of causes is such as to determine a change in the properties of the body generally, and render it subject to new laws, more or less dissimilar to those to which it conformed in its previous state (Mill 1973: 377).
20 The importance to the early emergentists of what we would call emergent laws rather than emergent properties is easily underestimated, especially in many more recent discussions which often take the truth of the Completeness Thesis as a premise. See section (3.1) below.
The image Mill has in mind for the heteropathic laws is that they ‘supersede’ the lower level laws (1843: 433-4), rather than contravening or violating them (I return to this point in section 3.2 below). A final point which needs to be noted with reference to Mill is that he regards his commitment to heteropathic laws as entirely consistent with his thorough-going determinism, since the net effect of all the laws in play in any given situation is always unique, and hence if we knew all the relevant laws and facts, we would be able to make successful predictions:21
If we could determine what causes are correctly assigned to what effects, and what effects to what causes, we should be virtually acquainted with the whole course of nature. All those uniformities which are mere results of causation might then be explained and accounted for; and every individual fact or event might be predicted, provided we had the requisite data, that is, the requisite knowledge of the circumstances which, in the particular instance, preceded it (1973: 377-78).
Mill’s account of emergentism is not an argument for the truth of that doctrine, but rather a case for the coherence of a certain view of the laws of nature. The question of whether there are heteropathic laws, and if so which ones, are entirely empirical as far as Mill is concerned. In what follows I will take the main outlines of Mill’s position as paradigmatic of emergentism, and for the most part (except in the discussions of Bhaskar) focus on the problem of what evidence can be brought to bear on the question of the defensibility of emergentism thus conceived. A few brief observations about contemporary emergentism may help make clear why little of significance is lost by thus focussing on Mill.