Metaphysics and the mind/body problem

If you have browsed through the shelves of popular book stores such as Barnes and Noble, you may have come across a section labeled metaphysics. Within this section, there are books about witches, UFOs, ghosts, and crystal healing. Within the academic study of philosophy, metaphysics deals with very different kinds of topics. In this post, I will explain what philosophers mean by ‘metaphysics’ and compare it to the science of physics. I will also argue that theories in physics—as well as the other sciences—make metaphysical assumptions. 

Metaphysics deals with questions about the nature of reality. Here are some of them:

Ø  Why is there something rather than nothing? 

Ø  What is the relation between minds and brains? Are minds and brains one and the same? Can minds exist without brains or are they dependent upon them?

Ø  Are future events just as real as the present or the past events? 

Ø  Do numbers exist?

Ø  What is the world ultimately like? Does science give us a complete and accurate description of what there is, or is there much more to reality that what we can observe? 

 The word ‘metaphysics’ goes back to the time of Aristotle, translating roughly to beyond or after physics. While I have not heard the discipline of metaphysics characterized like this before, I think that it can also be understood as a prequel to physics. Before engaging in theories about the physical world, you will likely need to have some views about the nature of reality. Reality is what the world is really like, whereas science tells us about the observable physical world. One may ask what the difference is between the observable world and reality. Aren’t they the same thing? Plato often made a distinction between appearance and reality. Large buildings may look very small when we are far away, but they in fact aren’t. Science gives us better tools for examining the world and its contents, but those appearances may be deceiving as well. The world may be very unlike how our current (and future) scientific theories describe it to be, and it is possible that we may not be able to know what the world is really like. Putting such skeptical worries aside, it is still intelligible to say that there are (deeper) facts of the matter. There is a way that the world is, and metaphysics is a discipline that actively tries to figure out the details.

 Rene Descartes in his book ‘Meditations’ tried to establish a firm foundation for science by reflecting upon the metaphysical views one may think it presupposes. For instance, science presupposes that there exists a physical world (made up of discrete objects) that is external to the minds of human beings. Descartes tried to defend such views by appealing to the existence of God, whereas philosophers such as George Berkeley tried to deny them, maintaining that everything that exists is mental in nature. On Berkeley’s view, there simply are no objects ‘out there’ in the world, it’s all in our (and God’s) mind. Likewise, philosophers such as Spinoza deny that the world is made up of discrete objects. On Spinoza’s view, there is only one thing in the world—the universe itself. The universe is comprised of many (possibly infinite) parts, and passes through various stages (or as Spinoza called them ‘modes’), but it is ultimately one highly complex object. The views of Berkeley and Spinoza may sound very outlandish, but it a matter of ongoing scholarly debate as to where exactly they go wrong (if they do at all). With respect to 1) whether the world is physical or mental, and 2) whether the world is one or many objects, science can carry on undisturbed. The truth or falsity of such metaphysical theories can be thought of as running parallel to scientific theories. Scientists may sometimes rightfully ignore metaphysical issues, but there are instances where science runs deep into metaphysical waters. 

Two of our best scientific theories (i.e. quantum mechanics and general relativity) run into problems of interpretation. By problems of interpretation, I mean that the experimental data is compatible with a multitude of metaphysical hypotheses (11 to be exact). To give just two examples, the many worlds interpretation states that there are an infinite number of branching universes, whereas the Bohmian interpretation states that there is only one universe. At the moment, it is thought by many physicists and philosophers that there is (in principle) no scientific test or observation that could favor one interpretation over another. But surely, only one of these interpretations can be correct. The world can only be one way. There have been different reactions to the problem of many interpretations. Some scientists reserve judgment, others argue for one interpretation over the others, and some adopt a position known as ‘instrumentalism’. Instrumentalism states that science is in the business of making accurate predictions and models, not informing us what the world is really like. Perhaps the instrumentalists have got this right. If science cannot tell us what the world is really like, maybe metaphysics and philosophy can. 

It is believed that most (if not all) metaphysical questions are to be solved through careful thought and logical analysis, rather than through observation and experimentation, two of the central investigatory tools of science. Scientific findings may inform the discussion, but they rarely answer metaphysical questions by themselves (*though most scientists believe the exact opposite is true!). Metaphysical views are compared with one another in terms of their overall plausibility, their compatibility with other theories, logical coherence and on measures of elegance and simplicity. To understand how metaphysical debates are carried out, I will focus on the relation between the mind and the brain. If we are to appeal to science alone, what kind of experiment or observation might determine whether minds and brains were one and the same?

 Let’s say that future scientists perfect brain imaging. Furthermore, let’s stipulate that such technology allows scientists to pinpoint the source in the brain for all mental activity. Your emotions are correlated with brain activity in region X, while your personality and moral character are correlated with brain activity in region Y, and so on. Could we conclude from such observations that the mind is simply identical to the brain, and that, for instance, there is no immaterial soul? Not from experimental data alone. Even perfect correlations between brain activity and mental activity do not establish causality, though it does provide one with good reason for thinking they are causally connected. Substance dualists, whom believe that the mind and brain are distinctly different kinds of things, will argue that the experimental data shows how the physical brain is affected by the immaterial soul. It doesn’t conclusively demonstrate that there is no soul. 

How can one rule out the possibility for there to be a soul causing all of the activity in the brain? Since the soul is said to be immaterial—i.e. not located in space—there would be no way to scientifically test for its presence. Instead of relying upon experimental data or observations, philosophers have offered several arguments for why there probably isn’t an immaterial soul. The first style of argument appeals to scientific theories and laws. It is argued that 1) the alleged causal interactions between souls and brains violate laws of conservation of energy and 2) are in conflict with Einstein’s relativity theory. 

A second style of argument is conceptual in nature. Such arguments question the coherence of mind-to-brain causation. If a mind is not located in space, and is not made up of anything physical, how does it interact with a physical brain located in space? Let’s suppose that the soul causes the brain to feel guilty about an immoral action. We can give a nice story about what goes on in the brain during such an experience, but what happens before the moment of soul-to-brain interaction? How does the soul initiate the sequence of brain activities? In everyday causal interactions (e.g. knocking over a glass of wine), objects typically interact through direct contact. My hand makes contact with the glass and then the glass falls off the table. But it doesn’t really even make sense to say that the soul ever “contacts” the brain since the soul does not occupy any space. The soul must interact with the brain in some other way. But given that the soul and brain have no properties in common (other than existing in time), it is hard to see how any kind of interaction is possible. Rene Descartes, an early proponent of substance dualism, conceded that this problem of causal interaction was a powerful objection to the view, and ultimately, was unable to give a satisfactory reply. At this point, a dualist might appeal to mystery. Just because we do not know how the causal interaction is possible doesn’t mean that it’s impossible. Soul-to-brain causation might just be beyond human comprehension.  

Lastly, a third style of argument appeals to a principle of logical reasoning called Occam’s razor. Occam’s razor states that you ought not multiply entities beyond necessity. Put in everyday English, if you have a theory that explains everything by positing one thing (e.g. the brain), then you shouldn’t posit something else (e.g. a soul) in addition to it. Positing additional entities runs the risk of error. A theory is more likely to go wrong if one starts adding extra parts that are unnecessary. For example, take a theory of electricity that appeals to electric demons. The theory is otherwise identical to modern theories of electricity, but insists that the flow of electricity is maintained by sprinting immaterial demons. What should we make of such a theory? It is clearly absurd to posit such entities to a theory because the demons don’t add anything to the explanation. If anything, they just complicate it for no good reason. The same is thought to be true of the addition of a soul to modern psychological and neuroscientific theories. Scientists and philosophers alike argue that we can explain everything without positing a soul on top of the highly complex organ that is the brain. Dualists might insist that there are certain things that psychology and neuroscience leave out. For instance, our subjective experience of the world. How can brain cells and chemicals give rise to consciousness? 

In closing, I have argued that there a subset of meaningful questions that science alone cannot answer. The distinction I’ve implicitly made between science and philosophy may be challenged. I’ve taken science to comprise the activities that scientists regularly engage in (e.g. observation and experimentation), and metaphysics—as a sub-branch of philosophy—to be the activities that philosophers regularly engage in (e.g. conceptual analysis, logical reasoning). I do not want to say that there isn’t a great deal of overlap between science and philosophy. On the contrary, I think that the two disciplines are entangled together. There are times in which we are all philosophers, and times in which we are all scientists. Philosophy and science are intellectual activities that human beings practice to better understand the world and their place in it. When we entertain purely metaphysical questions, we have our philosopher’s cap on. When we perform experiments, make predictions, or analyze data, we have our scientist’s cap on. Metaphysical questions have been lingering for millennia and offer no easy solutions. But each of us will likely find one of the (many) solutions to be plausible or, at the least, not as crazy as the rest.