Will neuroscience ever replace philosophy of mind?

The basics of the mind-body problem

The human being as a cultural being or an object of nature?

The mind-body problem has a long history in our culture. Many will first think of the philosopher, mathematician and physiologist René Descartes (1596-1650). This conceptually separated bodies (or extended things) and souls (or thinking things) into two domains. These are connected to one another in humans - and only in them - primarily in the pineal gland (epiphysis). Because of its central location in the brain, this organ seemed to Descartes the right place for the body-soul interaction.

But I would like to go back almost exactly 2000 years longer in our cultural history, namely to none other than Socrates (469-399 BC). After his conviction for wrongdoing to God and pernicious influence on the youth, he sat in prison and waited for his death. With his critical questions he had turned too many Athenians against him.

His students and friends, including Simmias from a well-to-do family, wanted to enable him to escape. But Socrates stayed. And he remained calm, true to his ideals, even though he considered the verdict to be unjust. This is what the literary tradition of his pupil Plato wants. And there in the prison his students Phaedo, after whom Socrates' last teachings are named, Simmias and Kebes, visited him again.

One reason for the composure of the philosopher, while many of his friends were already mourning him, was his unshakable belief in the immortality of the soul. Even today, almost 2500 years later, it is not surprising that people think about the afterlife in the face of death. But this is not about Socrates' theory of the soul.

Explanation of social issues

For those of us who remain indefinitely in this world, another interesting question arises: Why was Socrates in prison? Or, more generally, what counts as Explanation for facts like the fact that the philosopher stayed there - and hadn't fled with his friends?

Socrates says that even in his youth he was interested in the causes of all phenomena. In doing so he came across the work of the natural philosopher - there was no natural science in today's sense - Anaxagoras (500-428 BC). According to his teaching, the answer to the question why Socrates is in prison is

because my body is made of bones and tendons, and the bones are dense and separated by joints, but the tendons are arranged to be attracted and slackened, and the bones are surrounded by the flesh and skin that hold them together. Since the bones are now rotating in their joints, if I let go and tighten the tendons, I am now able to move my limbs, and that is why I am sitting here with my knees bent.

Phaidon, 98c-e, based on a translation by Friedrich Schleiermacher from 1809

In short, from today's perspective we would say that Anaxagoras is the facts reduce to the physiology wanted. The attempt is similar, explains Socrates further, to reduce the conversation between him and his students to sound, air and hearing. But he strongly contradicts such efforts and instead considers it to be the "real causes"

that because the Athenians liked condemning me better, it seemed better to me to sit here, and seemed more just to stay here and patiently take the punishment they ordered. Because, with dogs, for a long time, I think at least, these tendons and bones would have been in [the port city] Megara or with the Boiotians ... if I hadn't thought it was fairer and more beautiful than that I should flee and go away, the state to atone for the punishment he orders me.

Phaidon, 98e-99a, based on the translation by Friedrich Schleiermacher from 1809

In other words, Socrates was imprisoned because of the Athenian judgment and because of his own decision because he thought it was fairer and nicer than running away. And one has to admit, almost 2500 years later, that there is a certain plausibility inherent in this explanation. However, trying to explain on a physiological level why the philosopher sat there and would drink from the poison cup a little later instead of enjoying his freedom in Megara would still be an insoluble challenge today.

Welcome to the heart of the mind-body problem.

The formal mind-body problem

It is true that we are now talking less about souls than in Socrates' time - not in philosophy, and certainly not in the natural sciences. But, as I would like to show below, there is also talk of the "spirit" (English at least, from Latin mens and Sanskrit manas), which we encounter more often in philosophy or the "humanities", is not without problems. Up to this point, however, it should have become clear that to this day it has remained a challenge to describe man as a cultural being or as an object of nature; and this challenge has accompanied us at least since ancient times.

The British philosopher Jonathan Westphal wrote a new book in 2016 on the mind-body problem - or in its more recent version it should better be called the "mind-body problem" .1 In it he formulates it as a logical problem with the following four premises:

(1) The mind is a non-physical thing.
(2) The body is a physical thing.
(3) Mind and body interact with each other.
(4) Physical and non-physical things cannot interact with each other.

The four assumptions lead to a contradiction and therefore cannot be true at the same time. In a similar formulation of the problem by the Swiss philosopher Peter Bieri, I will go into the meaning of the individual premises and the contradiction in more detail. Here I want to first of all draw attention to seeing the mind as a "thing". In technical language, this is also called reification, literally "reification", from Latin res for "thing".

Whether we speak of "Geist" in German or use the English "mind", as Westphal does in his book, we should pause for a moment to see what we mean by that. The Duden explains the word as "the thinking consciousness of man, intellectual power, understanding", the Grimm dictionary puts it in a total of 119 columns in relation to the soul and the breath, among other things. With over 500,000 characters, a single word entry would be enough for your own book! But that would be of interest to a few linguists and philosophers.

For our purposes, it is sufficient to state that one first makes the mind into a thing and then later gets into trouble because physical and non-physical things cannot interact with one another. One expects something from the spirit understood in this way, which, according to scientific considerations about, for example, energy conservation or cause-effect relationships, it cannot achieve. No wonder that leads to trouble!

Enigmatic interaction

World affairs are more complex than what happens on a pool table. There one ball meets another, transfers its kinetic energy and the game continues. If you now set "the spirit" for the first ball, then it is not clear where and how the interaction, the push, should take place. Descartes was already confronted with this problem, as is documented in an exchange of letters with Elisabeth von der Pfalz (1618-1680). The noblewoman wrote to the philosopher in May 1643:

How can the soul of the human being, the spirits of life [German for Latin spiriti animalias the force that moved the body was called back then; Note St. S.] to carry out the arbitrary actions (since it is only a thinking substance)? This is because it appears that all movement is caused by an impact, the nature of the impact depending on the properties and shape of the surface through which the impact is performed. In the first two cases, contact is assumed, and in the third, spatial expansion. But you exclude this completely from the concept that you have of the soul, and it seems to me to be incompatible with an immaterial object. Therefore I ask you for a more specific definition of the soul than in its metaphysics.

Elisabeth of the Palatinate

Elisabeth pointed out to Descartes that he could not explain the interaction of body and soul. Yes, the philosopher cannot even make plausible how something immaterial can push particles in the body and thus set them in motion! Descartes' answer did not satisfy the noblewoman either, and she showed him further problems in his model of thought.

If today, almost 400 years later, we replace "soul" with "spirit", then the solution is by no means more obvious. Nevertheless, it is often tacitly accepted when someone formulates sentences like the following, to quote Westphal once again: "Matter or the physical can somehow influence the mind; and the mind can somehow move the physical body." 2 Another example provided the Canadian philosopher Walter Gannon in a recent article on psychiatric treatments:

Normal mind-brain interaction enables people to adapt to the world. In more severe psychiatric disorders, there is dysfunction on both the mental and neural levels. An adequate explanatory model for these disorders and interventions to treat them requires an understanding not only of the mind-brain interaction, but also of how genetic, epigenetic, hormonal, immune, and environmental factors affect that interaction.

Walter Gannon

Problems of dualistic language

Glannon believes that he has overcome Descartes' body-soul dualism, but continues to use dualistic language in which the soul is simply replaced by the spirit. Westphal and Glannon are not alone in this; and it's not just philosophers who talk like that.

For example, a quick search for "the mind" on Google's academic page, Google Scholar, yields nearly four million hits. And on the Web of Science, a database for scientific articles, a corresponding topic search provides thousands of publications. In addition to philosophy, psychiatry, psychology, neurosciences, humanities, literature and history are at the top of the list.

In early human history - and in some religions until today - it was customary to describe inexplicable natural forces as gods: there was a god of water, fire, rain or thunder and so on. This process is also called "deification", deification. Do we do the same when we ascribe our psychological processes such as perception, feeling, thought, decision and action processes to a spirit, reification?

How should we prove the existence of such a thing? We cannot touch it, move it back and forth or bombard it with physical particles. To quote a famous phrase from the Hindu Bhagavad Gita (Chapter 2, Verse 23), one of the most important books of this religion, with which the self is characterized: "Weapons cannot harm it, fire does not burn, water does not do it wet and wind doesn't make it dry. " This seems to be the case with the mind too. So do philosophers and scientists often talk about an illusion?

The Bieri Trilemma

I want to approach my proposed solution with an intermediate step. Above I promised to deal with Peter Bieri's variant of the mind-body problem. This was taught to me in my studies and I still use it in my own teaching today. In the following, however, I have replaced "mental states" with "psychological processes":

(1) Mental Realism: There are genuinely mental / psychological processes and these are non-physical processes.
(2) Mental causation: Mental / psychological processes are causally relevant for the course of the world.
(3) Causal closeness: The physical area is causally closed; every physical event has a sufficient physical cause.

This formulation is similar to that of Westphal, but only has three premises. This is mainly due to the fact that the British philosopher explicitly defined the body as a "physical thing" in order to make the logical contradiction more easily recognizable. Before I get to the contradiction, i.e. the mind-body problem in the narrower sense, a little more should now be said about the content of the three assumptions:

Mental realism grants psychological processes their own right to exist. They are fundamentally different from physical processes. In any case, this corresponds to our intuition that our perception, feeling, thinking, decision-making and acting is something that only occurs in the living part of nature, in a more demanding sense only in the higher living beings and, in the most demanding way, perhaps only in us humans. (Representatives of computer intelligence or artificial consciousness may forgive me for leaving this topic aside in order not to make the essay too long.)

The idea of ​​mental causation expresses that psychological processes not only arise as by-products, but also have an effect on the world. This also corresponds to our intuition, because we experience our decisions and actions as results our perception, feeling and thought processes. It can hardly be doubted that our actions, such as my writing this article now, make an impact in the world, for example your reading it. The question here is whether the actions really have causal consequences more psychic Processes are. Maybe the whole causal interaction only takes place on the physical level?

Now the third assumption remains, that of causal closeness. Whole volumes have been written on the question of what causality is. We cannot deal with the subject in such depth here; But we don't need that either. We can leave it at our intuition that the network of causes and effects in nature and especially in physics does not have any gaps. Every physical event then has a complete physical cause. (The fact that the principle of causality in physics has lost its importance due to the discovery of quantum mechanics would be a justified objection, but does not mean anything for the mind-body problem.)

Long philosophical discussions can be held about each of the three premises, and scientific findings can also be referred to. For us it is sufficient here that they are not completely absurd, and the assumption of two excludes the third: If psychological processes are non-physical and yet causally effective, how can the physical area be causally closed? After all, the consequences of our psychological processes, for example the typing movements of my fingers on the keyboard, are yes also physical processes, namely ultimately the movement of atoms.

If, instead, one assumes mental causation and considers the physical area to be causally closed, how can psychological processes still be non-physical? And finally, thirdly and lastly, if psychological processes are non-physical and the realm of the physical is causally closed, how can they still have a causal effect? It seems hopeless: every time we come up with a contradiction. Based on the word "dilemma" and the name of the author, this formulation of the mind-body problem was also called the "Bieri Trilemma".

Three classic solutions

Interestingly - and this is what makes the Bieri Trilemma so suitable for teaching - you can assign any attempt to get rid of one of the premises to a certain philosophical standpoint: If you reject mental realism, you end up with a reductionist position, the comes down to the fact that psychological processes are ultimately only physical processes. Formulations such as: "The mind is nothing other than the brain" are examples of this. Extreme positions generally deny the meaning of the speech about the mind or psychological processes. This is why this is also called "eliminativism", which includes the word "eliminate".

If you reject the thesis of causal unity, you usually end up with dualistic viewpoints. The main question that arises is to what extent psychological processes still fit into a scientific world model. As we have seen, Descartes, for example, gave the soul its own mode of being, that of the thinking substance. He also assumed that it acts on the body (and vice versa), primarily through the pineal gland. But he could not explain the postulated mechanism of action, not even make it plausible.

Finally, one can reject the thesis of mental causation. This point of view is then called epiphenomenalism.An epiphenomenon is a mere marginal phenomenon, a consequence of other processes that have no effect of their own on other processes. A classic proponent of this point of view was the biologist and philosopher Thomas H. Huxley (1825-1895), who incidentally continued Descartes' physiological ideas and applied them to humans.

Even today some philosophers, biologists and neuroscientists take the position that there are psychic processes in a strong sense, but that these cannot have any influence on the physical level. This degrades the mind or the psyche, if you want to call it that, to a mere spectator of world events.

Incidentally, Huxley was not only the grandfather of the biologist Julian and the writer Aldous Huxley, but also a great defender of Darwin's theory of evolution. While Charles R. Darwin (1809-1882) stayed out of public debates, Thomas Huxley did not avoid confrontations with influential church representatives. This earned him the nickname "Darwin's Bulldog", for which he is probably better known today than for epiphenomenalism.

More detailed analysis of the language

We have already learned a lot - but still no solution to the mind-body problem. I think we can look more closely at that language have to deal with, which we are using here.

Most of us would probably agree with the thesis that we have processes of perception, feeling, thinking, making decisions and acting. For example, I can now see the text on the screen, hear a car drive by outside, but also see the green leaves of many trees through the large window and hear the chirping of birds. It is a sunny day in May.

I know that I sit too much at the computer and that's why I already feel pain in my neck, shoulder and arm. But I have made up my mind, among other things, to finish this text before June. I started the first version over a year ago. Since I already wrote my master's thesis on this topic in 2005, my expectations of myself are high: I really want to take a step further. And it should also be a nice text.

These factors - at least that's how I experience it - all play a role in the decision to write these lines now. I don't want to stop until I'm done and think with nonsense of the university online course I have yet to teach tonight. I had already forgotten him; then it occurred to me whether I could skip him. My students do that sometimes. But as a course instructor, I can't afford that.

I am linguistically referring to part of these processes by speaking of the decision to write the text. Most readers will probably also easily understand what I mean by that. But if I have to specify an exact point in time when this decision will take place, I will run into problems. I would even say that this process has dragged on for days. It is a struggle with myself that will only come to an end when this text is finished.

Scientific research

Anyone who wants to scientifically investigate such phenomena, which are undoubtedly part of our world, is faced with many problems: The linguistic formulation that I have proposed here is much too crude. No experimental psychologist or neuroscientist can do anything with a description like "the decision-making process is an internal struggle that has dragged on for days". I used to do experiments like this myself.

In order to be examined with the usual psychological or neuroscientific methods, a process must be standardized and limited in time, ideally in a time window of a few seconds. Due to the variability of measurement results, it must ideally be producible on instruction and repeatable many times. Such challenges have to be mastered before is started with an attempt at all.

Then the question arises as to what kind of measurement method is used to investigate the phenomenon. Electroencephalography (EEG) has been used for almost 100 years, measures electrical currents on the scalp and is very fast, but spatially rather imprecise. Newer methods such as functional magnetic resonance imaging (fMRI) are spatially more precise, but very slow in terms of time. It also measures a blood flow signal that is only indirectly related to cell activation in the brain.

Nobody would doubt that the nervous system and especially the brain play an important role in the processes mentioned. The nervous system is also located in a body and the body is in an environment. Past processes are also decisive for the state of the body and the environment. Descartes must have been that far and even Socrates admitted, as we saw at the beginning of the article, that in a certain sense his bones brought him to prison.

What do we want to explain?

But what do you have to explain? Let's imagine a more recent example of a bank robber standing in court and being asked why he robbed the local savings bank on a particular day. His answer: "Because the motor cortex of my cerebral cortex sent signals to the muscles that made me go to the savings bank; signals to my hands made me wave the gun and signals to my diaphragm, my vocal cords and my mouth let me shout: 'Get some money or it'll pop!' "

In a certain sense, the robber's explanation is correct, because we know from testimonies and video recordings that this is how the deed happened. In a certain sense, the description would also be scientifically correct, because all these processes must have taken place in the body for the bank robbery to take place. The court would still likely believe the bank robber was kidding or not taking the questioning seriously.

This example makes it clear that our everyday phenomena and also the explanations in our society are of a very different kind from the phenomena that researchers investigate in the laboratory and their explanations. In individual cases, as here, the declarations ultimately accepted can have a major impact, for example on the sentence. Due to the limitations of their experimental approach and methods, psychologists and neuroscientists can only examine one small piece of the large and colorful human mosaic. And that is often challenging enough!

For comparison, let's think of the three-body problem from physics: Even when predicting the orbit of three celestial bodies on which gravity acts, our mathematics (so far) has reached its limits. The behavior of these objects appears chaotic to us, even if the forces acting on them are deterministic. A simulation can only be used to find approximate solutions, so to speak by trial and error.


The adult human brain has around 86 billion neurons, which often have many thousands, sometimes even tens of thousands, of connections to other nerve cells. There are also other cell types, the function of which is still not entirely clear. There are also complex control loops that can activate or suppress cells. However, even a few nerve cells behave chaotically, in other words in such a way that even the best scientists can no longer predict their reactions. There is no change in sight for the time being.

So even if Socrates' decision in favor of the poison cup and against fleeing, even if my decision in favor of writing the text and even if the bank robber's decision to rob the savings bank was completely determined in the brain, we simply cannot scientifically cause it - Specify the chain of effects on the neural level. Whether we will ever be able to do so is pure speculation.

What is certain, however, is that we would lose important information if we gave up the everyday explanations: Socrates wanted to remain true to his ideals, I wanted to meet the deadline and the bank robber wanted more money in order to achieve certain goals.

It is a characteristic of our everyday language to be able to use an expression such as "the decision to do X" to express a situation and put it in a context that actually took place and also has an explanatory function. The language of science is more precise in terms of its claim, but inferior in this explanatory context because the underlying cause-effect relationships are inaccessible, at least for the time being.

A computer comparison

For comparison, let's imagine a modern computer: In order for a program to be executed by the processor, it must be available in machine language at a certain point. This is the language, so to speak, that the processor understands. For us humans, however, this language is rather unsuitable, so that we have to use a certain programming language, at least for more complex programs. A certain program, a so-called compiler, translates this into machine language for us afterwards.

If something goes wrong during the execution of the program, the processor has executed the instructions in machine language. From a certain level of complexity, however, it is simply no longer realistic for people to explain the error on this level. To do this, the application must be examined in the programming language, changed if necessary and then recompiled (translated) into machine language. The programming language thus has a certain explanatory and useful function that cannot realistically be replaced by the machine language, even if the processor actually only executes machine language.

Extreme reductionism

Let's compare this to what the theoretical physicist Sean Carroll wrote a few years ago:

All we need to explain everything we see in our everyday world are a handful of particles - electrons, protons and neutrons - that are created by some forces - nuclear force, gravity and electromagnetism - and according to the basic rules of Quantum mechanics and general relativity interact with each other.

Sean Carroll

Carroll works at the renowned California Institute of Technology, is one of the leading physicists in his field and is also very active in science communication. Here he is now claiming that one can explain our entire everyday world in the language of physics, with only three types of particles, three types of forces and a few more rules. If that were true, not only would the entire humanities, cultural and social sciences and psychology, but even neurosciences, biology and chemistry be superfluous.

The physicist advocates an extreme reductionism, which, given today's knowledge, is obviously wrong and rather improbable in view of the progress of science. But various neuroscientists made similar statements when they claimed to be able to explain the whole human being from the brain. Interestingly, these scientists would also be unemployed if the even more radical view of the theoretical physicist Carroll were correct.

Think for yourself how far you would still get in your life if you could only talk about electrons, protons and neutrons and their interactions. And this also applies analogously to brain research and psychology: These investigate and explain certain subsystems of humans, we think of movement, hearing, seeing or speaking. An explanation of the big picture fails, however, due to both experimental and methodological limitations.

Useful everyday language

But our everyday language is so useful precisely because it is imprecise to a certain extent. Physiologically there are infinitely many ways to put the mobile phone on my desk: more from the left, from the right or from above, sometimes faster, sometimes slower and so on. These all fall under the a Description: "Stephan took the mobile phone on the desk."

For the context and the understanding of why I did this, namely to check for new short messages, the differences on the physiological level are irrelevant. Similarly, examining Socrates' bones cannot answer the question of why the philosopher stayed in prison and did not flee to the port city of Megara.

Our everyday language may be fuzzy. But it is not wrong. And this blurring is what makes them so useful. There is nothing wrong with wanting to make the language more precise. But you shouldn't lose sight of what you're trying to achieve with it. Likewise, someone can try to explain the errors of a computer program in machine language. There may be a few special cases in which this makes sense. As a rule, however, this will waste time. And what gain in knowledge does that bring? We also already know today that the nervous system plays a decisive role in processing perceptions, feelings, thoughts, and in making decisions and acting.

In the end, let's come back to the body-mind problem: The search for body-soul or, more modernly, body-mind interactions is nonsensical, because these are not two different things like two balls on the pool table. The centuries-long search for this interaction was pointless because the question was wrongly phrased. Quite a few philosophers, psychologists and neuroscientists believe that they have left the mind-body dualism behind, but actually still speak in dualistic language.

My proposed solution

The problem can be solved as follows: There are psychic processes because psychic descriptions do not always work, but often enough, and describe facts of this world in a meaningful way. Of course, physical, brain physiological, and even physical processes can be assigned to these processes in specific individual cases.

But that doesn't help us in practice because we can't even describe the processes on this level. In particular, we cannot use it Contexts of meaning create questions such as, "Why did Socrates stay in prison instead of fleeing?" Or "Why was Stephan typing on the computer instead of letting the sun shine on his stomach in the park?"

The next time a neuroscientist comes and says: "You are nothing but your brain!", Then we should reply: "Oh yes? Then explain this and that." And in addition: "Haven't you heard what leading physicists say? They are nothing but electrons, protons and neutrons! I can expect more precision from a scientist."

Philosophers have also tried to be more precise and have identified, for example, intentional and phenomenal content as decisive characteristics of psychological processes. The former means that they are about something, for example Socrates' punishment, my text or your wishes; the latter relates to what it feels like to have this process, the subjective experience content. Some philosophers have reified this and speak of "qualia" as if they were small atoms of consciousness that exist somewhere in the space-time continuum. I fear that this reified language will again cause us more problems than it explains anything.

The missing subject

However, the philosophical considerations underline one important point: Psychological processes - at least those in a richer sense - are always processes of someone, a subject. That is why I think it is problematic that, in the course of the 20th century, leading branches of science, such as psychology and brain research, banished phenomenology and introspection from their realm as "unscientific". A part of the human being can be explained from the outside view, but not everything.

Many laypeople have also understood this and therefore prefer to choose literature on Eastern philosophies that have not carried out the subject-object separation. Or they prefer the philosophy of life and phenomenology over standardized quantitative studies, which admittedly proceed according to today's conventional rules of science, but ultimately clarify facts that are irrelevant for human life.

By the way, ancient philosophy was not yet so torn and was in the midst of life. For Socrates, however, this was fatal. So should he have published in highly specialized journals, the meaning of which hardly anyone understands? So all that remains for me is to come back to the Bieri Trilemma and resolve it as follows:

(1) Mental instrumentalism: There are genuinely mental / psychological processes as long as their descriptions relate to facts in the world.
(2) Mental creation of meaning: Mental / psychological processes are necessary for the understanding of meaningful connections in the world.
(3) Causal irrelevance: Causal explanations are overrated and of little relevance to the advancement of many branches of science.

The conclusion is that man is both a cultural being and an object of nature. There is no contradiction here.And it remains a fascination how the consciousness experiences and cultural achievements of the human being can arise in a body and in particular in the 1.5kg cell tissue and connections of the brain. Instead of wanting to reduce "the mind" to physical processes, one could also turn it around: body is mind.

The world can fascinate you both philosophically and scientifically.

This article also appears on the author's blog "Menschen-Bilder".

(Stephan Schleim)

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