An introduction to the defence against neurobiological reductionism

It was whilst studying neuroanatomy during my third semester at medical school that I first came across the problem of neurobiological reductionism. We had three weeks to prepare for this fourth and final part of the cadaver dissection course, and so I delved into the realms of our brain and spinal chord, the ‘central part’ of our nervous system, learning about the various lobes, the basal ganglia, the limbic system, the brain stem and so on. It wasn’t until learning about the frontal lobe, which includes the prefrontal cortex – a structure that’s widely held responsible for many of the characteristics that separate human beings from all other living things- that I began to think about the meaning of such understanding for the concepts about our own actions, and indeed for free will in itself. An often used example when explaining the functions of the prefrontal cortex is the tragic story of the young American railroad construction worker Phineas Gage. He was the head of a small unit of men within the rail company, described by those who knew him as extremely capable; an excellent worker as well as a respected leader. During an accidental explosion in 1848, an iron rod was knocked into Mr. Gage in such a way that it ‘entered on the side of his face, shattering the upper jaw, and passing back of the left eye, and out at the top of the head’1, cutting in its path through the connections between limbic system (held responsible for motivation and human drives) and the prefrontal cortex. It didn’t, however, damage his brain stem, and he was thus left alive. To the general astonishment of medics at the time, Phineas Gage recovered fully from the accident. He was able to see with his other eye, his vital organs worked normally, he was able to walk, talk, eat, drink and appear generally like a well-functioning human being. Yet emotionally, Mr. Gage changed. He became erratic and uninhibited in his behaviour. He lost his job and his friends. His post-accident behaviour was compared to that of a child. Anatomically, everything still worked the way that it should do, except for the damaged connections within his brain. The prefrontal cortex was cut off from the limbic system, and this showed in his behaviour. Interestingly, it has often been claimed that Mr. Gage later managed to relearn some of his social capacity- the changes were apparently not permanent.

When given some thought, the story of Phineas Gage is a threat to our common sense concepts of self, for it shows how dependent we are on the structure of our anatomies in the formation of our most intrinsic qualities. We live in a day and age where science has lifted the big secrets; we have made endless progress in biology and physics, in chemistry and astronomy, and we have shone light upon the secrets of the human body. Since Darwin, the scientific world accepts evolution and natural selection. At the same time, the ideas that we as a race have of ourselves have also slowly changed, from being God’s most loved creatures to less romantic realisations- towards seeing ourselves now as the products of a process that dates back millions of years and that could be explained just as well as the structure of a molecule of oxygen, given sufficient time and research. In short, we have reinvited ourselves as the products of explainable processes, and thus the products of physical processes; steps that can be measured and explained using the resources that have been available on our planet during the course of our evolvement. If we are to accept Darwinism and natural selection, and to accept that we are tied into evolution just as tightly as all other species on our planet, then we must also accept that we are bound inseperably to a physical world. The most useful term for describing this concept is ‘physicalism’- a thesis which argues ‘that everything is physical’2.

Wy worry about physicalism? The authors of ‘Did My Neurons Make Me Do It?`, which seeks to find counter-arguments to the depressing argument that will be discussed, introduce their work as follows:

‘If humans are purely physical, and if it is the brain that does the work formerly assigned to the mind or soul, then how can it fail to be the case that all of our thoughts and actions are determined by the laws of neurobiology? If this is the case, then free will, moral responsibility and, indeed, reason itself would appear to be in jeopardy.’3

In current-day mainstream thought, a physical world would entail the brain taking the place of what we used to think of as the soul. Many people- especially those who have been convinced by theories such as the big bang and evolution- have slowly dropped the idea of a soul, and are in its place looking towards the sciences for new explanations. The brain, like the heart and the lungs or a building or space rocket, can be described in terms of the stuff that it’s made of- in terms of the physical constituents that we can see and touch, the lowest level of these being atoms. Newtonian laws have taught us about forces, and we have a very specific concept about causes and effects. One thing knocks another, and then causes something else to happen, and so on, the result being a whole chain of causes that could all be traced back to some prior event. Films such as ‘the butterfly effect’ (which is also a concept in chaos theory) play upon this idea; a common example being that the flap of a butterfly’s wings in one part of the world can cause a hurricane somewhere else. And if the brain were to take the place of the soul, if the brain could be held truly responsible for all thoughts and actions, then how could it indeed ‘fail to be the case’ that everything we do is predetermined by physical things, in this case by brain events? If this were the case, we would begin our lives with an initial ‘setting’ of brain tissue, with specific neural connections. We would then react to each and every stimulus during the course of our lives, both in the womb and after birth, in a determined way, the connections changing as a result of each outer influence, but no single action ever being truly free, for our brains would be ‘set’ to respond in a specific way. A useful image of this sad world is perhaps a few billion intertwined railway tracks: Each of us as a small train, heading on their individual track from start to finish, from birth to death, looping up and down and taking shortcuts and detours, but always on their own track, meeting others, yes, but within a personal predetermined destiny. Broadly, this tragic scenario is what is meant by `neurobiological reductionism`- it reduces us to predetermined physical things, the product of the constituents that make up our bodies, where the concept of free will becomes nothing but an illusion.

Neurobiological reductionism is something that we intuitively disagree with, because we each have a deeply embedded feeling of being the master of our own actions. To say that we simply don’t believe in the concept will not be very useful in discarding of the theory- a reductionist will argue that the illusion of free will is created through consciousness, but that we never truly choose what we do. It is not a theory that I am willing to accept, however, not at least until all other approaches have been exhausted. Reductionism changes the very essence of what it means to be a human being. And so what we have to try to do is to find flaws in the reductionist’s approach- to find explanations for free will, if it indeed exists, that work within a physicalist world.

This search will be a long process of re-thinking the ideas that we take for granted. I have not yet found the absolute answers, but Murhpy and Brown offer convincing ideas for a more positive outlook. Most interesting for me is the concept of dynamic systems; that is, systems that are constantly changing and inseperably intertwined with their environment. It is important to see the human being not as dualist thing with a brain and a body, with a wall separating it from the environment. Rather, let us begin to think of ourselves as a body with a mind that are inseperable from each other, and that are in turn connected at all points with the environment, such that there is no clear border or barrier. In a closed system, such as a roulette table, in which we know the position of each part before an action, it would indeed be possible to predict the exact position of each part after the action, provided that we have complete knowledge of the conditions. This roulette table would seem to have only bottom-up causation. The things at the bottom, the constituents of a thing, in this case 37 coloured pockets, a ball, a wheel and their respective initial velocity, position and direction could be used to predict exactly what will happen at the higher level- the game of roulette. In contrast to this, Murhpy and Brown introduce top-down causation, which they apply to dynamic systems. This would work not instead of, but in addition to bottom-up causation. According to this theory, a system cannot be explained simply in terms of its constituents. Top-down causation claims that the higher level that is created out of its parts is capable, in turn, of having an influence on its constituents. If this were true, dynamic systems would no longer be reducible to the sum of their constituents, for they would also have a downward effect on their parts. Something new would be created here, something that could not under any conditions be followed back through the channels of causation.

Murphy and Brown use the example of an ant colony to illustrate a dynamic system. The ant colony is made up of a variety of ants which fulfil numerous indiviual roles. Each ant is tied into this colony with a certain predeterministic character- they are each led chemically towards their goals, they are programmed to fulfil roles within the colony. They are, arguably, the slaves of a combination of their senses and the environment, with no ability to choose freely what to do. Yet the colony itself is a system that develops over a period of time that is longer than the life-span of a single ant (a single one of its constituents). Each ant is part of a system that is formed in a bottom-up manner. But the level at the top, the ant colony, also has an effect on the behaviour of the ants- an effect upon its constituents.

Similarly, a human being’s turnover of the ‘stuff’ of which it is composed is said to be between seven and 10 years4. This means that every single atom in a human being is replaced within a certain time frame. We are still the same person, with the same line through history, with memories that date back to a time when we were made entirely of other constituents- a dynamic system which is, on the one hand, dependent on its constituents, for without the atoms that make up the cells which make up muscular tissue, which in turn makes up the heart, we couldn’t exist. Yet the system as a whole also has an effect on its parts, and the parts themselves are replaceable. Within this dynamic process lies a truth that is helping us to find the flaws of the reductionist approach, along with an already rich and ever-increasing bundle of evidence for free will that can co-exist with physicalism.

1The Boston Post, September 21, 1848

3Did My Neurons Make Me Do It? Philosophical and Neurobiological Perspectives on Moral Responsibility and Free Will. Nancey Murphy and Warren S. Brown