In Mind, Brain, and Free Will Richard Swinburne argues from the epistemic interstice between our knowledge of quantitative states of matter and that of qualitative states of consciousness to an ontological dualism of material and immaterial substances. It is a development, in greater detail, of the argument presented in chapter 3 of The Evolution of the Soul.Footnote ¹ From this ontological dualism he further deduces that human beings are essentially immaterial and indivisible subjects of mental events. He then proceeds to reason to the probable, but less than certain, truth of the libertarian account of freedom of the will, and from that to a realist account of moral responsibility (presenting his case in terms of moral objectivism but allowing moral subjectivists their own reading).

I think the book is not merely of interest because it is a counter-cultural philosophical anthropology, at odds with the current materialism that inclines many to conflate physics and metaphysics. It is also important because it raises fundamental issues about starting-points and navigation-points in philosophy, and because there are practical consequences that issue from the conclusions.

First, there is the question of the starting-point. Although chapter 1 is entitled ‘Ontology’, Swinburne's argument to substance dualism is an argument from epistemology (we cannot deduce the content of mental events from a description of associated physical events) to ontology (therefore mental events belong in a different ontological category only contingently related to physical events).

He says that he wants to be able to tell the complete history of the world. Such a history would be a description of the sequence of events that constitute that history. Swinburne defines an event as the instantiation of a property in a substance at some time, a time being any period bounded by instants. But what counts as a substance, and what counts as a property, is relative to language; and so what counts as an event is relative to some description, and any event will admit of many descriptions. Therefore, what Swinburne needs is a single formula denoting all the properties instantiated in some substance at some time from which all other possible descriptions of that same event can be deduced; such a formula would be the canonical description of that event.

Our descriptions of the world are a matter of applying predicates (attributing properties) to subject terms (to substances). This is Swinburne's true starting-point, because it is our descriptions of the world that we test for truth; testing descriptions for truth presumes some correspondence between the terms used and the world so described. Any such correspondence is achieved by a designator. On Swinburne's account, a designator may be one of three types: a non-rigid designator; a rigid but uninformative designator; and a designator that is both rigid and informative.

A non-rigid designator is a description of a substance which is satisfied by the contingent properties picked out by the predicates of that sentence e.g. ‘the most commonly occurring potable’. A rigid designator is one with which a substance has been nominated, or ‘baptised’, irrespective its non-essential properties or the predicates which may truly but only contingently describe it. Any rigid designator therefore picks out the same substance in all circumstances. An uninformative rigid designator picks it out by the accidental properties of that substance e.g. ‘wateriness’ but an informative rigid designator nominates it by properties believed to be essential to it e.g. ‘H₂O’.

If Swinburne is to tell the history of the world by way of canonical descriptions (a subset of events) which entail all additional possible descriptions (entailing all events), then the canonical descriptions must use informative rigid designators i.e. designators such that to know what the word means is to know the conditions for its correct application. If informative rigid designators are required for canonical descriptions, then only designators that are logically equivalent will pick out the same property. He rebuts a posteriori criteria of identity: causally inert properties, principally phenomenal properties, such as ‘… is red’, cannot be reduced to contingently co-instantiated causally efficacious properties, such as reflecting light at 650nm. Nor can a mental property and a physical property be the same property under different modes of presentation, the difference being one of sense but not of reference; because where there are two senses, there are two predicates, and hence two properties. Identity criteria are purely a priori on this account, and the criterion of identity is synonymy.

So, for example, ‘… is red’ does not mean: ‘reflects light at 650nm’; nor does it mean ‘stimulates primarily the L-cones of the retina’; nor does it mean the same as any of the sentences providing a true description of any of the electrochemical reactions occurring between the retina, the primary visual cortex, and the inferior temporal lobe into which neurons of the visual cortex extend. However detailed the physical description, ‘… is red’ cannot be deduced from it; and because it cannot be deduced from such a description, the mental cannot supervene upon the physical. For one property to supervene upon another requires the possibility of deducing the presence of the supervening property from the presence of the conditional property.

What ‘… is red’ picks out is a mental property, and the mark of a mental property (according to Swinburne) is that it is a property that entails privileged access at all times of its instantiation. ‘Privileged access’ is the additional access the subject has to those events to which third-parties may also have access through other means. Whatever means third-parties may have of observing my having a red image, I can share; but I always have the additional access to that red image by virtue of its instantiation in me. In contrast, physical properties are those which entail no privileged access at any time of their instantiation.

Neurological research has important but, on Swinburne's argument, limited prospects. Each individual's brain is unique, and each brain is rarely if ever in the same state twice; mental properties – with the possible exception of raw sensations – have propositional content. The prospects for psycho-physical laws are therefore poor. Empirical data linking brain events and mental events may accrue in ever greater detail. Brain imaging may reveal to researchers that you are imaging a large white bird; but to know that you are intentionally picturing a swan and not a goose, they must ask you your beliefs and your intentions; mutatis mutandis for other patterns of sensation. Underwriting this conclusion is the logical divide between quantitative data (patterns of sensation, strengths of desires and beliefs) and qualitative data (the differing significance of similar sensations to different subjects, or the content of their desires and beliefs). It is inescapable, on Swinburne's account, that crucial to any neurological investigation of the mental life is one key component in the experimental method: asking the subject.

The primacy of the first-person perspective is thus a critical navigation point for Swinburne as he picks his way through the arguments of the physicalists. First, if third-person descriptions of events lack the possibility of deducing from them the data of phenomenal experience, then the description of the world Swinburne wants to be in a position to provide is incomplete. Secondly, it is the subject alone who experiences the world, and it is the data of experience that is the test of the truth of any description of the world. We even derive our concept of causation from our subjective experience of bringing things about; we do not retroject onto our actions a concept of causation derived from observing successive events.

Consideration of the phenomenal disunity of consciousness, drawn from cases of mental disorders and from the consequences of commissurotomies, does not support the conclusion that conscious subjects have the potential to fissure into two or more persons. Simpler explanations of dissociation, which preserve the unity of the subject and the economy of one person per brain, will always be available.

So, while it is true that the immediate causes of the different phenomenal properties I experience (colour, shape, smell, taste) are physical events in different parts of the brain, it is also true that I experience those different phenomenal properties as one conscious event (e.g. that red chilli pepper). Therefore, while we could trace the history of each part of a brain by identifying those parts through the phenomenal properties they cause, this would result in a false history of the world: it would falsely attribute different properties to different substances when in fact all the properties are co-experienced, and hence all are properties of what must be a single substance. This single substance must then be a mental substance because it is determined by co-experienced mental properties; and as it has no physical properties, it is a pure mental substance.

Furthermore, the simple theory of personal identity is true. Since ‘I’ and my proper name are informative rigid designators, then even in the specious present I can infallibly identify myself as subject to experience; so I can continue to exist even without memory (and, of course, on the present argument, without any continuity of brain matter). But, granting the soundness of the concept, what are informative designators as uttered by me of my experiences will cease to be so when uttered by me of yours: I stop at the traffic lights when I see them to be red; you may merely be conditioned to respond to light waves at 650nm by pressing a pedal. I am, essentially, a pure mental substance; and there lies the portal to solipsism, unless some of my experiences arise from interactions with the physical.

The principle of the conservation of energy, and hence the causal closure of the physical, is no obstacle to mental-physical interactions for the simple and sufficient reason that it is false: the principles of classical physics are true merely as statistical generalisations; and quantum mechanics reveals causal interactions without energy exchange. Swinburne considers at some length what might justify a belief in the causal closure of the physical and concludes that the only possible justification might be that at some future date it follows as a consequence of some as-yet unformulated high-level theory of physics.

This res cogitans that I am, it turns out, has a structure to its mental life. I have thoughts, beliefs, desires, sensations, and can form intentions or purposes. Thinking, at least sometimes, is something I intentionally do but at other times thoughts merely occur. (I consider thinking, on this model, akin to breathing: something I am hardly free not to do, but a process over which I can exercise some control.) I am caused to have the beliefs I have, but I can indirectly influence my beliefs by purposefully attending to relevant evidence; and I can similarly influence my desires, yielding or resisting occurrent urges and planning to satisfy or deny longer-term inclinations. Sensations are non-propositional mental events; Swinburne seems to accept a Kantian-like account of them as apperceptions. An intention, or purposing, is a meaning-to-bring about which can be efficacious in affecting bodily movement and which is always (like any thought) conscious. This economy of the mental life, previously presented at greater length,Footnote ² is a tidy-minded folk psychology.

The primacy of folk psychology is an aspect of the primacy of language that pervades Swinburne's case. Although he does not argue it explicitly, I think a case can be elaborated for such a primacy. The physical sciences have had to evolve technical vocabularies to name and describe objects and processes not evident to unaided observation: ‘atom’, ‘molecule’, ‘cell’; ‘covalence’, ‘gravity’. The development of the human sciences is different. Psychology in particular takes as its subject-matter phenomena long familiar to human beings who have evolved a subtle language in which to describe them. Hence, psychology has progressed by re-describing the familiar and then empirically testing those re-descriptions. The human agent thus becomes: a system of hydraulic-type ‘drives’; or an ‘operant’, the actions of which are ‘conditioned responses’ to ‘stimuli’; or an ‘information processing unit’, its sensations ‘inputs’ and its behaviour ‘outputs’. These re-descriptions are sometimes the models onto which the functional data of brain processes are mapped. However, any putatively scientific psychology or related neurology needs to refer back to the phenomena of thoughts, beliefs, desires, intentions, and sensations as these are captured in the language of folk psychology.Footnote ³ It is no different for physics. For physics, in analysing the world in terms of fleeting subatomic states, also needs to explain how it is that the tables and chairs and planets and stars picked out by the language of ‘folk physics’ appear solid and spatio-temporally continuous; because a physics which failed to account for such large-scale appearances would not be adequate. It is the phenomena captured by the language of folk psychology against which Swinburne repeatedly tests the claims of neurology: ‘Science starts from these data. We should alter our scientific theories to fit the data, not pretend the data don't occur’ (94).

These data suggest to Swinburne that the behaviour of human beings is the outcome of the relative strengths of reason (thoughts, beliefs) and desire (occurrent urges and stable inclinations). Brain-states are the proximate causes of behaviour but because the brain is rarely, if ever, in the same state twice there can be no fixed bias toward particular movements, and so no precise probability can be calculated pertaining to individual human actions. It is possible but not probable that future scientific discoveries will rule-out freedom of the will as a power of human beings. As things stand, quantum indeterminacy creates the space in the causal nexus for human beings, as pure mental substances, to influence their own brain processes to shape behaviour. However, only on an occasion when a human being is subject to a desire and a contrary moral belief is there an occasion for framing an intention to act contrary to inclination. On most occasions, intentions are permissive, allowing actions to proceed from desires according to the agent's beliefs. Hence, moral praise and blame attaches not to people's actions but to their intentions, modulated according to the relation obtaining between people's intentions and their moral beliefs. He is surely right that Libet-type experiments lack consequential significance sufficient to elicit any human capacity for freely choosing between alternatives.

There are therefore implied practical consequences to the philosophical anthropology delineated. Without the potential conflict of contemporaneous desires and beliefs in the same individual, the individual is a wanton. Only given the prospect of such conflict does the question of what to believe about the relative worth of competing desires have import.

Swinburne's case rests on fundamental philosophical theses: that logical necessity, possibility, or impossibility strictly implies a co-relative metaphysical status; that the principle of simplicity, and its subsidiary principle of credulity, is the best guide we have to truth; and that we can have justified beliefs based upon our experience, memory, and the testimony of others.

I wonder about the consequences of the principle of simplicity on the case laid out. On Swinburne's own account of simplicity it is a function of: the number of postulates; the number of different kinds of postulates; the familiarity and independence of the predicates used; the number of laws cited; the number of variables cited by the laws; and the mathematical simplicity of the values cited, and their number.Footnote ⁴ There are no psycho-physical laws, so the last two criteria are redundant. But is a world of two such very different types of substances in recurrent lawless interaction simpler than a world of quantities of mass-energy and four fundamental forces? The causal network of events becomes complicated: brain events cause brain events, and also mental events; mental events cause brain events and also other mental events; and there are logical relations obtaining between some mental states additional to the causal relations obtaining between them, as well as between mental states and brain states.

Swinburne, I think, would say that a world of mass-energy and four forces is insufficient for consciousness; that an immaterial substance is the simplest additional postulate possible to account for consciousness; and that there could be no more familiar predicates for describing the changes in that type of substance than those of folk psychology viz sensation, desire, belief, thought, and intention.

There are also intrinsic tensions within the account offered by Swinburne. If a mental property is one which is subject to privileged access at all times of its instantiation, then that does not fit well with his preferred account of desires and beliefs continuing to perdure when not consciously considered. If beliefs and desires are not identical with, or supervenient upon, brain-states then they perdure within the mind alone. If they perdure within the mind alone, then they are not actually subject to privileged access at all times of their instantiation. They are therefore not mental properties and, not being mental properties, cannot be instantiated in the mind. Swinburne himself is sensitive to this tension: ‘It seems evident, however, that brain events must also be at work in holding in place such a system of unconscious beliefs and desires’ (169). The conclusion that seems to follow is: sans brain, sans beliefs, sans desires, sans character; a res noncogitans.

Perhaps sensitive to the general direction of this kind of reasoning, Swinburne makes no mention within the present work of his modal argument to dualism previously presented and defended in The Evolution of the Soul.Footnote ⁵ In that argument he reasoned that the conceivability, and hence possibility, of surviving the destruction of one's body entailed the necessity of being a rational soul prior to such destruction. I think it a pity that he does not explain its absence, either by reason of its lying outside the scope of general reasoning exemplified in this volume or by providing brief obsequies if it is an argument he has come to abrogate.

Much the greater part of the work of the arguments deployed here is done by linguistic stipulations. Swinburne himself says that ‘any philosopher is entitled to define technical terms as they wish’ (71). Any physicalist counter-blast should therefore commence with alternative definitions, or explain why any such definitions should be abjured. At the very least, Swinburne's approach displays the virtue of such clarity. Professional philosophers will, I think, believe themselves to be familiar with the overall strategy of Swinburne's argument to substance dualism; but they should not let that familiarity dissuade them from engaging with the detail of the arguments deployed, because it is in the details that the strengths, and any weaknesses, of the book lie.