Physicalism is the thesis that everything that exists is just the physical. This claim is often made in the context of philosophy of mind entailing that the mental is just the physical. More specifically, minds are products of the activity of the brain. “Minds are simply what brains do” claimed American cognitive scientist Marvin Minsky . If the mind is just the brain, than many are wont to go one step further, concluding that they are in essence just their brains. They are but nothing more than a deterministic swarm of particles occupying a pink mass in their heads. Everything they are is contained in the activity of their brains and sustained by its continual activity. In this essay I claim that this view is deeply mistaken. You are far more than just your brain. Even accepting the physicalist thesis at face value, equating personal identity with the activity of one’s brain fails to be adequately explanatory.
Taking the physicalist claim to be true, the mind and the mental are supervenient on the brain. All thought, all cognition then must be part of the brain’s activity. Reasoning and rationalization, complex emotions such as love and hate, these are all processed via complex neural pathways. Memories are stored in synaptic connections and recalled through exquisitely complex mechanisms in order to help us function in our daily lives. Techniques in neuroscience such as optogenetics and fMRI help scientists to continually unravel the mysteries of the brain, decoding the complexity of our brain circuits and finding neural correlates of consciousness. Alternatively, in the field of deep learning, computer scientists build connectionist models that replicate human level visual classification. The overly optimistic scientist may declare that soon all mental activity and all of what makes us, us, will be explained away via neuroscience. This cedes far too much importance, however, to the brain. Parts of our individual experiences and information processing require things outside of our brains.
There is one sense in which the claim that we need more than our brains is trivial. Our brains are embodied; eyes, ears, noses, hands are all additional organs that provide sensory feedback to the brain. The brain requires information from outside of it. While this source of embodiment means there is more to you than just your brain, it is truly not an especially incisive claim. The devoted reductionist physicalist of the mind and personal identity doesn’t have to cede much here. Their claim could still possibly be mostly true, requiring little more than a few additional qualifiers on how the brain interacts with the world outside.
The reductionist view remains mostly intact, but embodiment of cognition digs deeper. Parts of bodies outside of blains play roles in information processing in ways that are more important than simple input output systems. Take as an example the cardiovascular system. The cardiovascular system provides oxygen to brain tissue via blood-flow. This is typically thought of as providing merely a metabolic role. Blood-flow to the brain provides fuel so that the brain may continue to function as normal, processing information in the way that it normally does. But the role of blood in the brain is greater than purely metabolic, it plays a role directly in information processing. In extreme cases this is obvious. Take the case of a localized ischemic stroke. Part of the brain suddenly ceases to receive blood as a result of a clot, and the effected tissue can no longer serve an information processing role. The brain does not necessarily cease operating wholesale, however. Rather, information processing capacities become limited and the individual likely suffers various ailments as a result. Clearly the cardiovascular system plays a role in information processing by allowing such processing to even occur. Away from pathological cases, information processing in the brain can be affected by physiologic differentials in blood flow to different parts of the brain. Differential blood flow affects information processing capabilities of different brain regions, thus playing an important role in cognition. Such processes can result in quite intricate effects on the brain’s activity . Besides such effects, the brain requires complex chemistry to function, not just complex connections between neurons. It is not far-fetched to imagine that metabolic regulations affect neural activity via mediation of the underlying brain chemistry. Indeed, diseases such as diabetes are well-known to have cognitive effects .
Here the reductionist physicalist may want to take another step and suggest that rather than being your brain, you are the sum collective of your brain and all of your body. Rather than the previous suggestion that you are your brain and your body its housing, you are just precisely your body. Unfortunately for him, this move will not work. The collection of an entire body is still insufficient to explain the phenomena we associate with humanity. Individuals are socialized in the world. Without an understanding of socialization we cannot explain behavior.
For the following discussion the physicalist is actually taken to assume an additional position besides pure physicalism. The physicalist is taken to assume a deterministic worldview: that the future of a physical system is strictly determined by the physical facts of the present. This assumption is not unreasonable, many physicalists would agree with determinism (at least at some level). Under the deterministic assumption, a human’s behavior, if they were just their body, would be predictable based on the state of all the atoms present in their body. This stance, too, is untenable.
Imagine a woman standing in her house. A man walks through the front door, walks up to her, embraces her, and says the words “I love you”. How will the woman act in the next instant? Prediction of her behavior requires additional knowledge on her social relationship with the man. If the man is her spouse, a likely action would be to embrace him back and say the words “I love you too.” If she does not know the man, her reaction would likely be quite different. This example is completely obvious and intuitive, but it illustrates the importance of social relationships in determining future behavior. A physicalist reductionist account of the woman cannot explain her behavior in terms of only the atoms that make up her body. Her social relationships must also be accounted for to predict her behavior. A physicalist reductionist account of the woman then would also have to provide a full account of her social relationships to understand her. The physicalist model requires an understanding of the man; two entire bodies must be understood in order to understand on. Take the above scene again, but place the characters in public park rather than the woman’s home. The change of location may change the woman’s behavior depending on her feelings on PDA. Social relationships, cultural norms, and locations all work together in predicting her behavior.
This sort of embodiment in the world carries beyond just other individuals and places. Take a pianist who goes home after work each day and plays their piano. Their behavior upon arriving home clearly relies on the presence of their piano in their house. If the piano is present, they will play. If the piano has gone missing, they will take a different route and likely call the police. The pianist is not explained merely in terms of their body. Indeed, they are not even explained in terms of their body, knowledge, memory, and skills. Explanation of the individual requires knowledge about their relation to an external object and knowledge of the status of that object. Likewise, the behavior of a financier on Wall Street will be affected by news of a change in inflation rates in Japan. The actions of other people across the globe affect her behavior via their relationships in society with her.
Indeed, for any individual there is much to explain about them. We all are socialized with friends, families, possessions, jobs, and social roles. Our behavior clearly depends on our brains, but our bodies cannot be ignored. Our roles and relations in society are just as important to understanding how we will behave as are our physical compositions. We are not simple closed systems behaving merely the laws of physics. Complex opinions, relationships, and beliefs guide us through our daily lives. Ineffable social forces compel us to behave in ways inexplicable in terms of simple physics or chemistry. A physicalist account of but a single individual would requires a physicalist account of all of human experience. You are an individual living in the sum total of humanity. You are not your brain. You are far more.
- Stoljar, Daniel, “Physicalism”, The Stanford Encyclopedia of Philosophy (Winter 2017 Edition), Edward N. Zalta (ed.), URL = <https://plato.stanford.edu/archives/win2017/entries/physicalism/>.
- Minsky, Marvin. “Minds are simply what brains do.” Truth Journal, INTERNET, http://www. leaderu. com/menus/truth2. html (1997).
- Moore, Christopher I., and Rosa Cao. “The hemo-neural hypothesis: on the role of blood flow in information processing.” Journal of neurophysiology 99.5 (2008): 2035-2047.
- Kodl, Christopher T., and Elizabeth R. Seaquist. “Cognitive dysfunction and diabetes mellitus.” Endocrine reviews 29.4 (2008): 494-5