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The mereological fallacy in Psychology: do you feel, or does your brain?

The mereological fallacy in Psychology: do you feel, or does your brain?

February 28, 2024

When you think of something that makes you go back to your memories of the past, Are you the one who reflects, or does your brain? Turning your attention to mental phenomena as internalized as memories can tell us that everything you do at that moment is limited to internal activity, something that the nervous system carries out.

But, on the other hand, could we not say that it is always the brain that thinks and feels, since all our mental life is linked to it? No need to stick to what happens when we remember: when talking to someone, the brain transforms concepts into words, right? In fact, we could even say that it is not the whole brain, but a part of it, that thinks and plans: what the prefrontal cortex does is not the same as what the medulla oblongata does.


If these questions have led you to think that your real "I" is really your brain enclosed in a set of muscles and bones, just as a machinist operates a cabin train, many philosophers, psychologists and neuroscientists would tell you that you have fallen in what it is known as a mereological fallacy . Let's go to the corresponding question.

What is the mereological fallacy?

Although the study of mental processes and the brain is very complicated, that does not mean that it is impossible. We currently have a level of technology that allows us to keep systematic records about nervous activity and behavior, which makes research lines that seemed like science fiction stories a few decades ago a reality.


Now, many philosophers would say that the revolution of technological advances that we have experienced in the second half of the 20th century and in what we have been in the 21st century has not been accompanied by a revolution of ideas comparable to the previous one; at least, in regard to our way of thinking about how the human brain and behavior work. Many times we fall into something that some philosophers have baptized as a mereological fallacy.

This concept was driven by the philosopher Peter Hacker and the neuroscientist Maxwell Bennett what is his work Philosophical Foundations of Neuroscience, pointed out an error that, according to them, had been committed by most researchers of the brain and the field of psychology: confusing the part with the whole. For example, affirming that the brain reflects, chooses, values, etc.

From the point of view of these two authors, the way in which mental processes conceive both most people at the popular level and many researchers in the scientific field is not very different from those who believe in a soul that, from somewhere of the brain, governs the body. Thus, the mereological fallacy is not technically a fallacy because it does not arise from an erroneous argument (although it is in the broadest sense of the term), but a failure when it comes to attributing a subject to a predicate.


Thus, to fall into the mereological fallacy is to attribute to the brain, or to some of its parts, properties and actions that are actually carried out by people. In the same way that it would be absurd to say that it is not the hawk but its wings that fly, it would be fallacious to say that the brain thinks, reflects or decides. We get carried away frequently by these assumptions simply because It is easier for us to understand how the mind works if we let ourselves be led by reductionism , and not because scientific research has shown that this set of organs reason or think outside the rest of the body.

That is to say, the mereological fallacy consists in understanding the human mind in a way very similar to what philosophers like René Descartes did to explain what the psyche is by appealing to the spiritual and the divine. It is an error with deep roots.

  • Related article: "The 10 types of logical and argumentative fallacies"

From Cartesian dualism to metaphysical monism

The study of the brain has been marked for centuries by dualism, that is, the belief that reality is composed of two substances, matter and spirit, radically differentiated. It is an intuitive belief, since it is easy to consider that there is a clear division between one's own state of consciousness and almost everything else, the "external" is very simple.

In the seventeenth century, René Descartes created a philosophical system that formalized the relationship between the body and the mind; just as he understood this relationship. Thus, the mind, the spiritual, would be seated in the pineal gland of the brain, and from there would govern the acts performed by the body. The precedent of the mereological fallacy, thus, was present from the beginning of the formalization of the scientific study of the brain, and of course this affected psychology and philosophy .

However, the openly declared dualism did not last forever: already in the twentieth century the monistic approaches, according to which everything is matter in motion, gained a hegemonic status. Philosophers and researchers who point to the existence of the mereological fallacy as a recurrent problem suggest that this generation of researchers he kept treating the brain as if it were a synonym of soul or, rather, as if he were a miniature person who controls the rest of the organism. That is why the mereological fallacy is also called the homunculus fallacy: it reduces human properties to small and mysterious entities that supposedly inhabit some corner of our heads.

Thus, although the dualism was apparently rejected, in practice it was still considered that the brain or its parts could be understood as an essence to which to attribute our identity. The monists used ideas based on metaphysics to change the name of the soul and baptize it as "brain", "frontal lobe", etc.

  • Related article: "Dualism in Psychology"
Giovanni Bellini

The consequences of the mereological fallacy

The mereological fallacy can be understood as a deficient use of language when it comes to talking about how mental processes really are and what the human condition is. Not coincidentally, Peter Hacker is a follower of the work of Ludwig Wittgenstein, a philosopher known for having argued that the failures of philosophy are actually inappropriate uses of language. However, falling into this fallacy means much more than not talking properly.

A linguistic error that can have consequences beyond the mere confusion of terms is, for example, look for parts of the brain responsible for thinking or making decisions , something that usually leads to analyze increasingly smaller areas of the brain. Recall that this, considering the existence of the mereological fallacy, would be like attributing to the axis of the wind mills the property of moving the blades.

In addition, this tendency is a way to continue believing in something very similar to the soul without calling it by that name. As a consequence, the belief that there is an essence from which our actions and decisions are born is still intact, and the body / mind dualism, or rejection of the idea that we are not fundamentally different from any other animal, is still there, disguised.

  • Maybe you're interested: "How are Psychology and Philosophy alike?"

A frequent error, automatic and unconscious

The concept of a mereological fallacy has not been accepted unanimously by neuroscientists or philosophers of the mind. John Searle and Daniel Dennett, for example, have been critical of this . The second, for example, states that it is possible to talk about "partial" actions and intentions and attribute them to the brain and its sub-systems, and that thus delaying the meaning of the terms "thinking" or "feeling" is not harmful. It is a point of view that bets on pragmatism, playing down the negative consequences of the mereological fallacy.

In addition, it can be thought that when it comes to talking about the brain outside scientific areas, either on a day-to-day basis or in dissemination, it is very difficult to talk about the functioning of the brain without doing it as we would do about of people. This has made it a relatively unknown idea: it describes something that we have been doing for centuries and that we do not normally see as a problem that affects us. Essentialism is something that is very attractive at the time of explaining all kinds of phenomena, and if we can reduce the causes of something to a clearly identifiable element and isolated from the rest, we usually do it unless we are attentive.

For the moment, then, it is difficult to find a way to talk about the mechanisms of the nervous system without automatically falling and without noticing it in the mereological fallacy. Doing so requires entering into preambles that few informative initiatives can resist, and have experience and training in philosophy and neuroscience that few people can afford. However, that does not mean that it is better to forget the fact that this problem is still there, that it is important to take it into account both in research and in faculties related to Psychology and Philosophy, and that the metaphors about how the brain works You have to take them as such.


Rethinking the Unconscious: Dissociation and the Question of Agency (February 2024).


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