The mind and body appear on first view to be very distinct entities, but yet they interact most strongly in some as yet unknown manner. The nature of these two entities and their interaction poses the mind-body problem. Here we consider various solutions to the mind-body problem and review what progress has been made to solve it.

A new look at the mind-body problem

The mind is composed of mental fragments – sensations, feelings, thoughts, imaginations, all flowing now in an ordered sequence, now in a chaotic fashion. There are also non-conscious components involved in early brain processing of stimuli (as in lower level processing in vision, such as in V1) or in emotions not yet in consciousness. On the other hand the body is constructed under the underlying laws of physics, and its components obey the well-enumerated laws of physiology. It is these characteristic differences between these two – between mind and body – that lead to the Mind-Body problem.

The Mind-Body problem has been in existence for several thousand years – going back to Plato, Aristotle, The Buddha and many other ancient Greek and Eastern thinkers. The problem is simple to state, even if the ideas of physics and physiology were not as well developed several thousand years ago as they are today: the mind and the body seem to be entities of very different kinds, so how do they interact so as to produce in a person a mind able to have effects on their body (as when the person wills the body to perform some act), whilst also their body can affect their mind (as in the experience of pain)? Although the problem is simple it has as yet no satisfactory solution, in spite of the amount of time and thought devoted to it over the millennia. But such excessive activity would be worth while if a universally-accepted solution were forthcoming, since such a solution would finally clarify the nature of our existence in the universe.

Much has been written on the variety of solutions to the Mind-Body problem. There are the dualist solutions (mind and body are distinct, although then the problem of how they interact becomes even more embarrassing, and is so far unresolved in any satisfactory manner); the idealist solution (there is only mind, and matter is merely a manifestation of mind, although how mind could have created the beautiful subtlety of the unification of the nuclear, electromagnetic and radioactive forces of nature, with a proposed extension (yet unproven) to fusion of those forces with the force of gravity through superstrings, seems impossible to comprehend); a third position is that there is only body or matter, so this is a reductive physicalist approach (but then how the amazing mental world full of our experiences is thereby created from matter has to be faced). There are also nuanced versions of one or other of these three initial positions for solving the Mind-Body problem, some having great sophistication and subtlety in themselves.

There is also the question of what exactly is the mind? It is certainly composed of conscious components, but it would also seem to contain non-conscious ones as noted earlier, such as unconscious emotions and low-level processing as yet out of consciousness; automatic motor responses are also below the radar of consciousness. These unconscious or pre-conscious components are not problematic since they do not possess apparently non-material private components like those that conscious components appear to do. A stone is not considered as having such private experiences as do we; it’s responses to action on it can be described in purely physical terms. Similarly the non-conscious processes in our minds can be accepted as arising solely from suitable brain processing, so more easily understood as components of the body (especially with the great advances in brain science tracking down and modelling in detail this pre-conscious neural activity). These non-conscious components of mind do not have (by definition) any conscious component, so there is no difficulty in expecting them to arise solely from brain activity: they can therefore be seen as on the body side of the mind-body duo. Thus the truly inexplicable part of the mind – that part to which the epithet Mind-Body problem most closely applies – appears to be that of consciousness. That position is appropriate to take here because it addresses what appears to be the most difficult part of the overall problem of mind-body interaction: how conscious experience can interpenetrate and fuse with bodily activity to affect each other in the way mentioned in the first paragraph. Detailed neural models of the other (non-conscious) components of brain activity are increasingly convincing such as for predictive value coded by dopamine, for motor responses guided by internal motor models, and for early models of visual and other sensory processing through a hierarchy of increasingly complex feature detectors; they clearly support the lack of any nonconscious mind-body gap. In support of the approach used here is that it is more in line with modern thinking on the Mind-Body problem, especially that brought to the fore by Descartes and since emphasised in the notions of the hard problem (Chalmers, 1996) and the explanatory gap (Levine, 1983); these specifically emphasise the gap between consciousness and brain activity.

The traditional mind-body problem

The traditional approaches to the Mind-Body problem were mentioned briefly above – the core concepts of dualism, idealism and physicalism, together with the numerous varieties in between involving mixtures and modifications. A set of references to these more traditional approaches are given at the end of this article (under General references to the mind-body problem). A brief expansion of this description is appropriate in any discussion of the Mind-Body problem.

Dualism supposes that there two ontologically distinct entities, mind and body. The distinction may arise from body and mind being composed of distinct substances (substance dualism) or from the same substance but with distinct functions (function dualism). The dualistic concept can be traced back to Zoroastrianism at around 1000 BC, and is involved heavily in parts of Buddhist philosophy as well as in modern religious beliefs.

There are numerous varieties of dualism: interactionism (where mind and body interact in a manner as yet completely unknown to achieve the apparent effects of mind on body and vice versa which were mentioned earlier), epiphenomenalism (where the mind is purely a pale shadow of the body, so an epiphenomenon, having no independent powers but being completely subservient to the actions of the body), parallelism (where the mind and body run along completely parallel tracks, again in a completely unknown manner, but leading miraculously to the synchrony between inner experiences and related bodily actions we observe in ourselves and others), and occasionalism (where mind and body occasionally hook up so as to produce the effects of mind on body or vice versa again as we experience, so being a limited form of parallelism).

One form of dualism is soul dualism, in which the soul is a part of the total human experience but continues after the death of the body. Such a feature was strongly represented in Ancient Egyptian religions, where the soul was considered as composed of several components, some of which died with the death of the body, others of which continued after the body’s death. It is also a commonly held modern religious belief. Important names associated with dualism are Plato, Aristotle, Descartes, Bishop Berkeley, Kant, Hegel and Bertrand Russell amongst many others.

Idealism, on the other hand, supposes in short that mind is all that exists, and the whole world is so composed. However there are numerous nuanced varieties of idealism, some brought forward to avoid the difficulties of other versions. The extreme version that all is mind is usually called subjective idealism or phenomenalism, whilst objective idealists propose that thought is the highest degree of reality. On the other hand another branch of idealism, that of panpsychism, consider that all objects of experience have minds; even more extremely, epistemological idealists claim that minds are aware of or perceive only their own ideas, not external objects.

Physicalism, at the other extreme, proposes that all of the Universe is composed of physical objects, and that even mind itself is created by some extremely subtle (and as yet unknown) mechanism of action between suitable physical components, most likely (according to modern ideas) situated in the brain. As for the other approaches to the mind-body problem expounded briefly above, there are numerous different varieties of physicalism: supervenience (where a given local distribution of matter cannot give rise to two different global patterns that are assumed to be instances of mind; this is to be regarded as a minimal form of physicalism), token and type (where the former assumes that for every particular event it can be identified with a purely physical event, the latter that every property is identical to a physical property), reductive and non-reductive physicalism (where the former involves a variety of assumptions on the manner in which statements of mental experiences are true if and only if some corresponding physical statements are true, whilst the latter is of the form of supervenience, for example, making no such strong assumptions), a priori versus a posteriori (where the claim of physicalism that all states of the world, including mental ones, can be derived from physical states, is given a priori or independently of experience, or alternately is a posteriori, so based on facts), and physicalism versus emergentism (where in the latter there is new knowledge emerging as mental states, such as described by psychology, for example, from underlying physical activity; more generally the mental is proposed to arise through an emergent process from underlying physical activity in matter).

Attacking the mind-body problem

We have seen that there are serious problems in the idealist or dualist answers to the mind-body problem. In the first case no idealist approach of any persuasion has even begun to explain the detail of the material world at the present level science has reached. The characteristics of the protons, neutrons and electrons which compose our bodies, and more especially of the quarks and gluons that compose them, is infinitely remote from an idealist world view. Nor does dualism seem to provide much help, although it does take the load from the idealist’s shoulders as to the intimate details of the construction of matter. Yet it throws little light on how the two different worlds – of mind and matter – interact. In spite of the increasing understanding of matter at ever shorter distances there is no hint of a corresponding enlightenment about how mind is constructed and more particularly interacts with that miniscule matter. Numerous questions arise such as does mind act on each sub-atomic particle independently or is there some sort of global mind-to-matter interaction? What about action in the reverse direction – of matter on mind? These and many similar questions have no answers. However there are likewise serious problems for the physicalist approach: the Mind-Body problem still faces brain science and philosophy like a nemesis. The global principles being painfully gleaned for the brain do not seem to involve any solution to this problem. That is because neuroscience has not explicitly led to any idea as to how and where consciousness arises in the higher-order brain processing achieved by attention and guided by emotion and long-term memory. More particularly there is no handle at all provided by brain science on the neural components that could support the I at the core of one’s self-attribution (for the Western phenomenologists owner/content division). This has led to a further set of problems – especially the ‘hard problem’ of Chalmers (1996), the ‘explanatory gap’ of Levine and the question of ‘what is it like to be a bat?’ of Nagel (Chalmers, 1996, Levine, 1981, Nagel, 1974) in the physicalist program. The first of these problems emphasises the intrinsic difficulty of understanding consciousness, the second that of how to get mind out of a stone and the third as to how can we appreciate the mental experience of other animals. None of these, as subparts of the mind-body problem, has had any accepted solution. If the mind-body problem cannot be explained satisfactorily through a brain-based approach as above, possibly expanding on the principles governing the brain, but always being able to be checked by scientific methods, then science will have failed in its attempt to explain all of the world. It would not have been able to answer in particular how mental experience is created from the activities of the apparently mindless nerve cells in interaction in the brain. Such a dramatic situation has not yet been met. Brain science is in its infancy, and even the principles adumbrated about how the brain processes information are still not agreed upon. The possibility of the creation of consciousness by brain activity is even more so. Thus we are still not in a position where the scientific approach to solving the mind-body problem has been seen to have failed. In any case it is fair to say that the mind-body problem is still unsolved.

Conclusion

We have given a brief survey of the variety of solutions to the mind-body problem that have been mulled over in the past. The problem still has no universally accepted solution. It is possible that modern brain science may make some progress in delineating how consciousness arises in the brain, and thereby will lead to further understanding. It is uncertain that such progress will ultimately lead to a solution to the mind-body problem.