Elements of metaphysics

by A. E. Taylor

§ 4. Epiphenomenalism. Of the three hypotheses which remain for discussion, the theory of Epiphenomenalism has the least to recommend it, and is open to the most serious objections. According to this view, all causal connections are exclusively between physical states. Bodily changes succeed one another in accord with uniform laws of sequence, which it is the province of the physiologist to discover, and every bodily change is completely determined by bodily antecedents. Certain bodily conditions are further attended by corresponding “states of consciousness,” but those states stand in no causal connection with subsequent bodily states, nor yet with one another. They are thus consequences or effects, but are never causes. The whole series of physical changes, from birth to death, which makes up the history of the human body, goes on precisely as it would if “consciousness” were entirely absent. This is what is meant by the assertion that all mental states are epiphenomena, superfluous accessories, which arise in the course of the connected series of bodily changes, but are entirely without any determining influence upon it. The doctrine may be diagrammatically represented thus a —— α
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b —— β
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c —— γ,

where the italic letters symbolise physical and the Greek letters psychical states, the vertical lines indicating the course of causal sequence.

If a psychophysical hypothesis were ever directly applicable to the actualities of experience, we might, of course, dismiss Epiphenomenalism at once as inherently absurd. For nothing is more certain than that in the actual life of direct experience our knowledge and our interests do determine the course of our actions. That what we believe and desire does make all the difference in the world to the way in which we behave, is one of those elementary verities out of which no scientific hypothesis can claim to reason us. Hence, when the defenders of the theory attempt to draw practical moral and juristic consequences from their doctrines, we are within our rights in simply declining to concern ourselves with so absurd a travesty of the simplest facts of experience. So long, however, as the hypothesis is put forward simply as a working hypothesis for the correlation of our physiological and psychological theories, the case is different. Its validity as a psychophysical theory must be estimated solely by the degree in which it renders this systematic correlation feasible, and is not necessarily impaired by the manifest absurdities which result from mistaking the doctrine for a description of actual life.

Now, if we look at the hypothesis from this point of view, we can at once see that it is really legitimate for some purposes. For the purpose of physiological science it is obviously to our interest that we should be able to deduce the later from the earlier stages of a physiological process. We have thus an interest in treating physiological changes, if we can, as unconditioned by any but physiological antecedents. And every actual success in establishing a uniformity or “law” of Cerebral Physiology is proof that the assumption that, for the process in question, the only determining conditions which count are physiological, is equivalent to the truth. The physiologist, then, is clearly justified in treating the psychical series as epiphenomenal, if he means no more by this than that he intends to deal, as a physiologist, only with processes which can be successfully resolved into uniform sequences on the assumption that they involve only physiological terms. Though whether any processes in the nervous system can be successfully treated as purely physiological sequences, nothing but the physiologist’s actual success in obtaining results from his initial postulate can decide.

If, however, the physiologist should go on, as he sometimes does, to make the assertion that not only can some nervous processes be treated as if their psychical accompaniments made no difference, but that they really are what they would be without those accompaniments, or even that all nervous process is what it would be without “consciousness,” he commits a gross logical fallacy. It is a mere blunder in logic to argue that because the presence of certain circumstances makes no difference to the special result which follows on a given antecedent, the result would equally follow in their absence. For it might be that in their removal the very antecedents in which we are interested would disappear. We are not at liberty to infer that, because the course of certain physiological processes can be computed without taking their mental correlates into account, they could occur apart from those correlates.

Even more serious are the consequences which follow when it is assumed that all mental processes without exception may be regarded as epiphenomenal, i.e. that all human action, if only our Physiology were sufficiently advanced, might be brought under laws of purely physiological sequence. Such an assumption would lead at once to the following dilemma: Either our Physiology must remain rigidly faithful to the fundamental postulates of mechanical science, or not. If it is faithful to them, its descriptions of human action must rigidly exclude all reference to teleological determination by reference to conceived and desired ends. I.e. we must treat human conduct as if it were fatally determined apart from any possible influence of human choice and intention, and thus stultify that whole work of historical and ethical appreciation which we have already seen to be the principal raison d’être of Psychology as a science. We must revert, in fact, to a theory of life which is identical with the extremest forms of Pagan or Mohammedan fatalism in everything except the name it gives to its ineluctabile fatum.[fatum.] Or, if we are not prepared to do this, we must allow Physiology itself to use the psychological categories of desire, selection, and choice, and thus covertly admit that human action, after all, cannot be described without the introduction of factors not included in the physical order. It is no doubt due to their realisation of this dilemma that psychologists are all but universally agreed to reject the epiphenomenalist hypothesis, while its popularity with physiologists may be explained by observing that physiological uniformities can manifestly only be successfully established for those processes which can be treated as if they were only physiologically conditioned.

§ 5. Parallelism. The hypothesis of Parallelism attempts, while preserving some of the characteristic features of the cruder view just described, to avoid its unsatisfactory consequences. Agreeing with Epiphenomenalism in the doctrine that physiological changes must be treated as determined only by physiological antecedents, Parallelism denies that the events of the psychical series are mere “secondary” effects of their physiological correlates. According to it, the series of physical and that of psychical events are strictly “parallel,” but not causally connected. Each event in either series has its precise counterpart in the other, but the physical events do not cause the psychical events, nor vice versâ. The successive members of the physical series form a connected causal sequence, independent of their psychical concomitants, while these latter, it is generally assumed,[^[177]] form a similar chain of causally connected psychical states. Thus every nervous change is determined solely by precedent nervous changes, and the corresponding psychical change by the corresponding antecedent psychical changes. In diagrammatic shape our hypothesis now takes the form

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a α

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