If Mind is Not Physical, How Can Mental Events Affect Physical Events?

When drawing up a division between the mental and the physical, if such a delineation exists, we must be careful to define the mind in terms that, as far as we can tell, are irreducible to the physical. This is no easy task, since there are many who believe that all thoughts, feelings and perceptions are but the firing of neurons in a certain way and in a certain part of the brain.

Nevertheless, there are certain properties we associate with the mind that we do not associate with any other entity; we can conclude from this that these are indeed features of mental states and not of physical ones.

The first of these properties is that of privileged access. This is the idea that one has immediate access to one’s thoughts and feelings in a way that one can only have of oneself. We can relate our thoughts and feelings to others, but this is merely second-hand information, and no matter how eloquent the speaker, one cannot make someone else actually experience those feelings. Further, the speaker’s words are filtered through the listener’s understanding and processed in a way that only the listener has access to.

Therefore one can be mistaken about events that take place “outside ourselves” and in the physical realm, but it is impossible to be mistaken about what takes place in our own mind. If I feel a pain in my foot, for example, even if the nerve endings in my foot are somehow mistaken and the pain is just an illusion, nevertheless I cannot be mistaken about feeling the pain.

Another criterion of the mental is the capacity for experiencing the world qualitatively. This means that, when one experiences a certain emotion, they are not merely replicating its effects, they are experiencing it as a quality. It is entirely possible, for example, to program a computer to replicate anger; however, it would only be replicating the outward effects of anger and not experiencing it qualitatively.

Even simpler phenomena cannot be reproduced in a computer (at least not yet). The recognition of a color would operate in a computer as it would in a human (by processing the frequency of the light), but a human mind would experience the color as well; a computer would merely process the data and match it up to its database. This capacity for qualitative interpretation cannot exist without a mind, and therefore is inexorably tied in with the mind.

Lastly, minds are capable of doing things deliberately. More specifically, we are capable of cognitive acts (thinking, remembering, etc.) and propositional attitudes (desiring, believing, etc.). Whereas other physical objects can do certain things (a rock can tumble down a cliff, for instance), they are incapable of doing those things deliberately, merely arbitrarily.

This fact allows us to ascribe meaning to actions committed by humans and not to those committed by mindless objects. If a rock tumbled down a cliff and killed someone we would not call the rock evil, because it didn’t intend to kill. Consequently, the capacity to have an intention, or to have propositional attitudes generally, is a necessary property of minds.

Dualism has for much of human civilization been the dominant view of the mind’s relation to the body. It was formulated most precisely by Descartes, but was originally proposed by Plato. The idea that the mind is distinct from the body seems to sit easily with our feeling that the mind transcends the physical world. As science has progressed, and the brain is increasingly seen in terms of neurons and synaptic gaps, dualism has become less and less dominant. However, one criticism of dualism that would have been valid even without evidence of such things is that, if the mind is indeed not physical, how can it possibly affect physical events?

One possible defence is that the interaction between the mental and the physical might not follow the model of Newtonian mechanics. It is theoretically possible that there could be an intermediate substance that is not mental or physical but can interact with both. There are instances of substances in the universe (such as dark matter) which, at least at the current time, science cannot fully explain.

By this rationale, why cannot the mind be of such a substance? Others (including Karl Popper and John Eccles) have proposed that, just as quantum mechanics has shown that events at a subatomic level are indeterminate, it may be possible that the same is true of events at the macroscopic level. Both of these proposals, however, are rather weak in that they depend on scientific principles but are thought up by philosophers who are not well-versed in science.

The comparison of the mind with dark matter is weak because, even if dark matter does not follow our established scientific laws, this does not mean that it is not physical. By definition, if the mind is not physical, then its interaction with the body cannot be explained by physics; if physics does not explain it then what does? The indeterminacy idea is plagued by vagueness – exactly how does the indeterminacy manifest itself? And why should it apply only to the mind and not to anything else in the macrocosm? Besides, many scientists have commented that the effects of indeterminacy cancel each other out at larger levels.

So far we have dealt only with substance dualism, a view which is particularly incompatible with science. Another form of dualism exists, called property dualism, which stands more firmly against purely scientific objections. Property dualism agrees that the mind is physical, but posits also that it contains properties that allow us to distinguish it from the physical (e.g. privileged access). The problem here is that, if the mind is physical, how can these supposedly irreducible properties come about physically in the first place?

To this challenge there have developed two different arguments, that of emergentism and epiphenomenalism. Emergentism argues that consciousness develops out of evolution. At one point in our evolution our brains mutated to accommodate consciousness; it was then apparent that this was to our biological advantage and so it prevailed. It is difficult, perhaps, to conceive of how this gives the mind separate, irreducible properties. In defence of emergentism, it can be posited that there are certain a priori concepts that would exist even if there were no physical world to substantiate them.

For example, a physical triangle needs atoms to be drawn on paper or even to be imagined, but the idea of a triangle as a shape with three straight, joined sides is completely independent, it seems, of physics. Therefore a triangle can be reduced to atoms, but is not conceptually reducible to them. We do not need physics to understand the nature of a triangle: our understanding of it relies on geometry – a science that cannot be reduced.

Epiphenomenalism argues that epiphenomena (thoughts and feelings, for example) are impressions left behind from neural processes. If one feels joy, the feeling is the echo or footprint of the neural process that accompanies joy. Further, while epiphenomena are caused by physical activity in the brain, epiphenomena cannot affect neural activity: the causal sequence only works in one direction. When one feels pain, the reaction is controlled by neural processes, and not by what we might think of as conscious thought.

This point of view is not without its problems, however. It seems rather difficult to argue that, if I am faced with a particularly tough dilemma, my decision on how to solve it comes as an automatic biological reaction and not as a conscious choice. Epiphenomena lists would argue that I am only given the illusion of choice. While there is no obvious way to prove logically that this is wrong, it seems to me that I am faced with a range of options and that I do not always choose in a predictable way according to my personality. I might even be aware that I am more inclined to choose one particular option over the others, and yet I am able to deliberately go against my instinct simply to show that I have the genuine capability of free choice.

As a form of dualism, property dualism is more convincing than substance. It is extremely difficult, without conjecture, to state that the mind is non-physical. If we follow the logic of Occam’s razor, why should we consciously create another factor to complicate the situation, especially one which we have no empirical evidence for? But property dualism does not rely on a literally non-physical mind, only a conceptually non-physical mind, in that we can think of it as irreducible.

While this view is open to attack from philosophers and scientists who ask, “how does an irreducible consciousness come from physical components?”, nevertheless it seems rather more intuitive to people than its absolute opposite – eliminative materialism – which denies that the mind should be looked at except in terms of atoms and neurons.