A.5 Conservative Animism
A.5 Conservative Animism
In this section I shall briefly sketch the evolution of attitudes to the completeness of physics since Helmholtz's promulgation of the universal conservation of energy. The issues are not straightforward, and there is no question of dealing with them fully here. But I would like to offer at least an outline of how the argument for the completeness of physics has developed since the mid‐nineteenth century.
Helmholtz's doctrine left various options open in relation to the completeness of physics. For a start, you could simply deny that the conservation of energy applied to animate forces. That is, you could hold that vital and mental forces are an exception to the general rule that all forces are conservative, and thus insist that the conservation of energy holds only when we are dealing with inanimate forces.
However, this option does not seem to have been popular among (p.250) scientifically informed commentators in the second half of the nineteenth century. The doctrine of the universal conservation of energy won widespread acceptance within a decade or two of its formulation. There is of course an evidential question here too: how far was this almost immediate agreement on the conservation of energy dictated by the strength of evidence rather than by intellectual fashion? But there is no question of pursuing this issue here. So let me assume for present purposes that the conservation of energy itself was well supported by the middle of the nineteenth century, and focus instead on where this left the completeness of physics. Certainly this is how the writers I shall discuss henceforth saw the matter. Their question was not whether energy is always conserved, but rather, whether such conservation leaves any room for animate forces.
As I pointed out in the last section, it is clear that conservation does leave such room. The universal conservation of energy may rule out indeterministic animate forces, but there is clearly nothing in it to preclude deterministic animate forces that do respect the conservation of energy. Even so, as I observed, Helmholtz and his young colleagues rejected any such special animate forces. It is interesting to consider what might have persuaded them of this. I suspect that they were moved by what I shall call ‘the argument from fundamental forces’. This is the argument that all apparently special forces characteristically reduce to a small stock of basic physical forces which conserve energy. Causes of macroscopic accelerations standardly turn out to be composed of a few fundamental physical forces which operate throughout nature. So, while we ordinarily attribute certain physical effects to ‘muscular forces’, say, or indeed to ‘mental causes’, we should recognize that these causes, like all causes of physical effects, are ultimately composed of the few basic physical forces.
It is possible that this line of thought was influential in originally persuading Helmholtz of the universal validity of the conservation of energy. We have already seen how Helmholtz's initial formulation of this principle hinged on the assumption that friction and other dissipative forces are non‐fundamental forces, macroscopic manifestations of processes involving more fundamental conservative forces. For it is only if we see macroscopic forces like friction as reducing to fundamental conservative forces that we can uphold the universal conservation of energy. Given this view about dissipative forces, a natural move would be to generalize inductively and conclude that all apparently special forces must reduce to a small stock of fundamental forces. After all, those special forces which have been quantitatively analysed, like friction, turn out to reduce to more fundamental conservative forces. So this could be seen as (p.251) providing some inductive reason to conclude that any other apparently special forces, like muscular forces or vital forces or mental forces, will similarly reduce.
Thus consider how Helmholtz argues in Über die Erhaltung der Kraft. He takes pains to stress how it is specifically central forces independent of time and velocity which ensure the conservation of energy. This emphasis on central forces (by which Helmholtz meant forces which act along the line between the interacting particles) now seems dated. Nowadays conservativeness is normally defined circularly, as a property of those forces which do no work round a closed orbit. This definition does not require a restriction to central forces. However, Helmholtz was in no position to adopt the circular modern definition of conservativeness. He was aiming to persuade his readers of the general conservation of energy, so needed an argument. It wouldn't have served simply to observe that energy is conserved by those forces which conserve energy. Helmholtz's actual claim was that energy is conserved by a wide range of known forces: namely, central forces. Still, this by itself doesn't show that energy is conserved by all forces, unless all forces are central. Why should this be? Well, as above, one persuasive thought would be that there is a small stock of basic central forces, and that all causes apparently peculiar to special circumstances are composed out of these.
It is clear from our earlier discussion, however, that this reductionist move is not essential to a commitment to the universal conservation of energy. An alternative strategy would be to allow that there are sui generis animate forces, and to maintain that these fundamental special forces are conservative in their own right. True, this position is open to the objection that there is no direct reason to suppose that any such sui generis animate forces will be conservative, if they do not reduce to other fundamental conservative forces. But this could be countered with the alternative inductive thought that, since all the other fundamental forces so far examined have turned out to be conservative, we should infer that any extra vital or mental fundamental forces will be conservative too.
Somewhat oddly, physiological research in the second half of the nineteenth century added support to this anti‐reductionist stance, by offering direct empirical evidence that if there were any special animate forces, they would have to respect the conservation of energy. In a moment I shall argue that physiological research has also given us strong reason to doubt that there are any special animate forces. But this latter conclusion derives from investigations at a microscopic cellular level, and such research had to wait until the twentieth century. Prior to that, however, there was a flourishing tradition of energetic research at a more (p.252) macroscopic level, which identified chemical and energetic inputs and outputs to various parts of the body, and showed that animals are subject to general conservation principles. Especially noteworthy were Max Rubner's elaborate 1889 respiration calorimeter experiments, which showed that the energy emitted by a small dog corresponds exactly to that of the food it consumes. (See Coleman 1971: esp. 140–3.)
The interesting point is that this kind of research did nothing to support the reductionist view that all apparently special forces reduce to a few basic inanimate forces. That normal chemicals are moved around, and that energy is conserved throughout, does not in the end rule out the possibility that some accelerations within bodies are due to special vital or mental forces. It may still be that such forces are activated inside animate creatures, but operate in such a way as to ‘pay back’ all the energy they ‘borrow’, and vice versa. Rather, research like Rubner's would have added weight to the position of those who took the existence of sui generis animate forces to be consistent with the conservation of energy, as further items in the category of fundamental conservative forces.
As exemplars of this position, I have already mentioned Leibig and Müller, two eminent physiologists of the older generation, who continued to accept vital forces, even after the conservation of energy had won general acceptance. And Brian McLaughlin, in his excellent article on ‘British Emergentism’ (1992), explains how the philosophers J. S. Mill and Alexander Bain went so far as to argue that the conservation of energy, and in particular the notion of potential energy, lends definite support to the possibility of non‐physical forces.13 (The ‘British Emergentists’ discussed by McLaughlin constituted a philosophical movement committed precisely to non‐physical causes of motion in my sense, causes which were not the vectorial ‘resultants’ of basic physical forces like gravity and impact, but which ‘emerged’ when matter arranged itself in special ways. The particular idea which attracted Mill and Bain was that these ‘emergent forces’ might be stored as unrealized potentials, ready to manifest themselves as causes of motion only when the relevant special circumstances arose.14)
(13) Indeed this line of thought seems to have become extremely popular in the late nineteenth century. The idea that the brain in a repository of ‘nervous energy’, which gets channelled in various ways, and is then released in action, is a commonplace of Victorian thinkers from Darwin to Freud.
(14) Not all emergentists were as sophisticated as Mill and Bain. In Mind and its Place in Nature (1923), C. D. Broad addresses the issue of whether independent mental causation would violate the conservation of energy (pp. 103–9). But instead of simply claiming that any mental force would operate conservatively, he insists that the principle of the conservation of energy does not explain all motions, even in physical systems, and so leaves room for other causes. He draws an analogy with a pendulum on a string, where he says that the ‘pull of the string’ is a cause which operates independently of any flows of energy, and he suggests that the mind might operate as a similar cause. While it is not entirely clear how Broad intends this analogy to be read, it is difficult to avoid the impression that he has mastered the letter of the conservation of energy, without grasping the wider physical theory in which it is embedded.