Abstract
Among Christian academia, few names command as much respect as Richard Swinburne. For over fifty years, the Oxford don has helped to initiate a revival in natural theology and breathe new life into academic discussions surrounding libertarian freewill and substance dualism. Unfortunately, painfully little of Swinburne’s publications have been targeted to non-specialists. By contrast, the release of his most recent work is a refreshing condensation of Swinburne’s defense of Cartesian dualism presented to a layman’s audience. As one would expect, Swinburne’s thesis, that human persons are essentially soulish beings who inhabit nonessential bodies, proceeds in a series of analytic steps.
Chapter 1 presents Swinburne’s general argument and postures it against the predominant physicalist interpretations of the human-mind relationship. Swinburne helpfully puts technical terms and their definitions in bold type throughout his work as a quick reference for the philosophically uninitiated. Chapter 2 takes advantage of this strategy by defining the long list of terms, such as ‘person’, ‘substance’, and ‘property’, which comprise Swinburne’s arguments. The latter half of the chapter then targets various forms of both non-reductive and reductive physicalism ranging from behaviorism to supervenience theory. He concludes that the failure of physicalistic attempts to reduce private mental properties to public physical properties leads to the conclusion that there are two kinds of substances: mental substances which are defined by their private, mental properties and physical substances which are external and publicly observable.
Swinburne’s third chapter concerns personal identity and whether ‘being the same person’ is reducible to certain properties a person maintains through their life. One theory, deemed the complex theory of personal identity, claims personal identity is dependent upon certain features, whether mental or physical, that are conserved over the course of time. Swinburne rebuts this claim with an ‘arbitrariness objection’ (p. 52). If identity is grounded upon having some degree (say, 50%) of the same bodily or mental features as some past person, why is it this particular percentage and not, say, 49%? The choice of any particular ratio would appear to be completely arbitrary. Swinburne offers a second, more limited objection. Suppose a mad scientist divides my brain in half and replaces someone’s left cerebral hemisphere and another person’s right hemisphere with my divided brain. If identity depends upon a continuity of memories, then, theoretically, I should be both persons simultaneously since each subsequent brain would contain a large portion of my memories. Counterclaims, such as semantic indecision or that persons can have a ‘partial identity’, fail to overcome these two objections. Consequently, Swinburne concludes that a simple theory of personal identity, one claiming identity is not analyzable in terms of continuity with past mental or physical features, is the correct one.
Having established the inadequacy of complex theories of personal identity, chapter 4 can now present Swinburne’s central argument for Cartesian dualism. Swinburne first outlines Descartes’s original cogito argument for the substantial distinction of soul and body. Simply put, since Descartes could conceive of himself as thinking apart from his body, and it is incomprehensible to conceive of oneself as both thinking and not existing, then the self must be something distinct from the body and must have the essential property of thinking. Swinburne notes two errors in Descartes’s original formulation. First, it would imply that the soul exists only so long as it is thinking. Hence, a deep sleep or being knocked unconscious would destroy the soul. Second, Swinburne notes that Descartes has only shown the soul is sufficient for existence but not necessary. Consequently, Swinburne reformulates the argument to address these deficiencies. In his revised version, Swinburne argues that it is conceivable that while one is thinking, one’s body is destroyed. Since one cannot lose all their parts and still exist, the very conceivability of this scenario demonstrates that I am distinct from my body. Thus, the self must be a separate substance whose single essential property is the capacity for thought. Swinburne compares his conclusion to that of the great Thomas Aquinas’s, concluding that they are virtually identical in all but one minute manner. He therefore argues that ‘Thomist substance dualism’ (p. 83)—a term sure to provoke Thomas’s contemporary defenders—is an inferior version of Cartesian dualism.
In chapter 5, Swinburne addresses the possible objection that when I use the term ‘I’, I could be referring unknowingly to my brain. He distinguishes between informative and uninformative designators. The former denotes terms where we know the ‘logically necessary and sufficient conditions for something to be that thing’ (p. 90). If the term ‘I’ is an informative designator, therefore, the objection fails. Since my sensations are unique to me, I cannot fail to recognize them as my own. The term ‘I’, therefore, is an informative designator yet one unique to me since only I know what I experience. Hence, we are not uninformed about what we are referring to when we use the term ‘I’.
Chapter 6 tackles the issue of whether mental events can act as causes for other mental events or physical events in the body. Initially, the obvious answer seems to be yes; my belief in global warming, for instance, may cause my further belief that it is imperative that I reduce my carbon footprint. Moreover, these beliefs may be the cause of certain bodily actions, such as my choice to travel by bike rather than car this morning. Some scholars, however, maintain that mental events cannot have physical or mental effects; instead, they affirm the causal closure of the physical, arguing that any mental causation is illusory. Swinburne rightly notes that the thesis, ‘No mental events cause other mental or physical events,’ is self-defeating. Since this assertion assumes that the person believing it has certain reasons for this conclusion, it must presuppose that these prior beliefs are the cause of their ultimate conclusion. Hence, it must assume the very mental causation it seeks to refute. Swinburne’s final chapter is a collection of various other questions his conclusions raise. He asks and answers questions ranging from when a human soul begins to exist, whether souls can be ‘replaced’, how we should interpret multiple personality disorder, and whether science could ever devise a law for the causal relationship of soul and body.
There is much to commend in Swinburne’s effort. His argument, while complex, is comprehensible to any reader dedicated in following his exacting logic. The use of bold type face for more technical terms allows the reader to quickly reference them when they reappear later in the work. Finally, as would be expected, Swinburne’s analytic rigor is generally impressive. One odd exception is Swinburne’s treatment of the term ‘substance.’ Swinburne defines a substance as ‘a component of the world; a particular object or collection of objects’ (p. 9). Swinburne offers multiple examples including a desk, a person, and the Milky Way galaxy. Yet under this definition, I and my desk in front of me would together count as a single substance since we are a ‘collection of objects’. In fact, I and the building on the next street corner could equally be called one substance. Thomas Aquinas’s treatment of the concept of substance, which Swinburne regrettably mislabels as a form of substance dualism, would have greatly benefitted this particular area of the book. Additionally, it is unlikely that Swinburne’s critics will be swayed by his fifth chapter. While Swinburne has successfully shown we cannot fail to misidentify our own mental properties, this does not immediately entail we know all the necessary and sufficient conditions for our own existence. Could there not be further essential physical properties unbeknownst to us?
Nevertheless, Swinburne’s book offers an excellent primer for those venturing into the field of the philosophy of mind. While analytically dense, it is a rewarding read for those curious about the current status of the soul in philosophical discussions. Although it might not be the final word on substance dualism, it offers a powerful case that will surely further provoke the perpetual discussion surrounding the state of our souls.