[Editor's Note] Scientist Qian Xuesen once said: "Philosophy without science is lame, and science without philosophy is blind." How does philosophy explain the problems caused by the rapid development of science, especially cognitive neuroscience and artificial intelligence science? , What are the new theories?

In this article, Wu Dongying, a lecturer at the Institute of Philosophy, Chinese Academy of Sciences, sorts out several mainstream theories of metaphysics in contemporary mind and cognitive science, and hopes to form a research dialogue between philosophical theories and empirical science.

How can a psychic entity be anchored in a body if it is not in space? Why does the spiritual entity accelerate along with the body when the plane accelerates to hundreds of kilometers per hour? Image source: Official website of the University of Bergen, Norway

What theoretical contributions and advances does contemporary philosophy of science have in brain science, psychology, and cognitive science? How to evaluate the advantages of philosophy in strengthening and promoting scientific hypotheses and coordinating the coordinated progress of humanities and science? The discussion in this article hopes to arouse thinking and discussion among readers with scientific background.

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With the development of cognitive neuroscience and artificial intelligence science, our understanding of the nature of the human mind is getting deeper and deeper, and the urgency of interpreting theories of the human mind from a philosophical perspective has also been put on the agenda.

Metaphysical questions in psychology, cognitive science, and brain science include: Does the mind exist? What is (the nature of) the mind? What is the relationship between heart, consciousness and brain? If the mind is the brain, how is the mind different from the brain? Is it possible to use science to explain and understand consciousness? Can neuroscience tell us what consciousness is? How does the mind interact causally with the world? How does the mind have perceptual content about the outside?

The era of artificial intelligence is approaching, and understanding the human mind can help inspire innovation in artificial intelligence technology. But the human mind has some important characteristics that distinguish it from animals or machines. These characteristics and differences involve questions such as: Is the essence of the mind a computer program? Is it possible for a computer or artificial intelligence to think for itself? Can minds exist in different kinds of things like computers or robots?

This article will start from the problem of mind and body, sort out the key points and difficulties of various psychological theories, and propose the difficulties that the problem of consciousness poses to current scientific theories. Finally, we will establish a research dialogue between philosophical theory and empirical science to deepen the development of research on the nature of the mind.

To facilitate discussion, in accordance with most conventions in contemporary philosophical literature, this article defines and distinguishes the following professional terms in philosophy.

Distinguish all psychological phenomena into static mental states and mental processes, the latter including reasoning, memory, learning, recognition, conceptualization and other processes. The former can be further divided into intentional states and non-intentional states. Intentional states refer to states that take other things as objects, including beliefs, desires, hopes, likes, doubts, judgments, worries, thinking, etc. Non-intentional states include qualia, experiences and emotions.

Distinguish everything in the universe into entities and attributes. Entities refer to things that can possess (exemplify) attributes. Common entities include individual concrete things such as particles, cells, every living thing, planet, galaxy, etc. Attributes are also called universals, which refer to abstract things that can be possessed (examples) by multiple entities. , including numbers, colors, shapes, weights, biological species, relationships, virtues, beauty, etc. We can also temporarily use subject-predicate distinction to understand the difference between entities and attributes. What is a subject is called an entity, and what is a predicate is called an attribute. For example, "Snow is white" involves the entity "snow" and the attribute "white". Another example is "Cheknao is a cat" involves the entity "Cheknao" and the attribute "cat".

An "event" is defined as an entity possessing a certain attribute at a certain point in time. Two events are the same event if and only if the same entity has the same attributes at the same time. The so-called one attribute "causally" causes another attribute means that the possession of one attribute causally causes the possession of another attribute. "Causality" here refers to the causal relationship in the general scientific sense, such as "lighting a match causes fire to burn" or "smoking causes lung cancer", which is the same as the usage of cause and effect in these two sentences.

The so-called mind-matter problem discusses how the mind and matter (referring to physical things such as neurons, brains, and bodies) are connected. Therefore, the core issue is how the mind and matter interact causally. Of course, common sense already presupposes that there is a causal relationship between mind and matter.

For example, the free will and moral responsibility emphasized by moral psychology must presuppose that our physical actions are caused by psychological causation, that is, mind-matter causation. At first glance, the mind-matter problem seems to be a scientific problem. How the mind produces causal effects can only be answered scientifically. However, philosophers engaged in research on the philosophy of mind from modern times to the present have pointed out many difficulties in mind-matter causation, indicating that this problem may not be solved by scientific experiments.

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We begin with the question "What is the mind?" Following the distinction above, if minds are treated as entities rather than properties, this position is called entity dualism. Entity dualists believe that we can imagine that the mind exists independently of the body, but the mind is different from physical entities (such as nerves, brains, bodies), which occupy space and do not think, but the mind is a kind of entity that does not occupy space but can think. entities with feelings.

The modern philosopher Descartes advocated that the spiritual entity is the soul. This psychic entity exists in the brain, and although it cannot be explained by science, it can have a causal interaction with the pineal gland of the brain, thereby causing physical movements.

But this idea creates many problems. Since the spiritual entity does not occupy space, it cannot have a causal effect on the brain nerves in space, so this view is no longer tenable in contemporary science. And according to the law of conservation of energy, energy in a system cannot be generated without reason. However, as a spiritual entity that does not occupy space, since it does not exist in the system, if it has a causal effect on the brain, it seems to be extra energy that is not generated in the system, which violates the law of conservation of energy.

The more serious question is, if the mental entity is not in space, how can the mental entity be anchored in the body? Why does the spiritual entity accelerate along with the body when the plane accelerates to hundreds of kilometers per hour? Since it does not occupy space, it seems meaningless to discuss the spatial location of mental entities.

If one abandons entity dualism, one can also take a monist position and claim that there is only one kind of entity in the world. If such entities are physical entities, the position is called physicalism.

Physicalism is divided into strong physicalism and weak physicalism. Strong physicalism holds that all entities and properties are physical, and there are no mental entities or mental properties. This position is also known as eliminativism. Weak physicalism believes that all entities are physical entities, there are no mental entities, but there are mental attributes. This position is also known as property dualism. Idealism believes that there are only spiritual entities in the world, no physical entities, and the world is constructed by the heart.

Recently, some philosophers have proposed a special kind of monism, arguing that the most basic thing in the universe is some kind of meta-mental entity or entity that is neither mental nor physical, but this entity can produce mental properties and physical properties or entities. The former position is called panpsychism and the latter position is called neutral monism.

Before introducing property dualism, we must first introduce the concept of "reduction" related to the mind-matter problem. For example the attribute "as an unmarried man" can be reduced to the attribute "as a bachelor". The so-called reduction of mind-matter attributes means that mental attributes can be reduced to physical attributes. Since the body can produce causal power, so can the mind.

This can be further broken down, if mental properties are reduced to behavioral properties, this position is called behaviorism. If the properties of mind are reduced to the properties of brain and nerves, this position is called mind-brain identity theory. These two positions are also known as reductive physicalism.

Behaviorism was popular in psychology in the middle of the last century. Influenced by the scientific trends of the time, only objects that can be observed through objective scientific experiments are science. The goal of psychology is to predict and control behavior, and the brain or subjective state is a black box. Pain, for example, is characterized by certain behavioral patterns or tendencies: shaking, sweating, rapid heartbeat, tears, and wailing sounds. Since the mind is behavior, the problem of cause and effect between mind and matter is naturally resolved.

But the problem is that the mind is obviously not an objective physiological reaction. Pain is a subjective feeling in the heart, not an observable physical reaction. Philosophers have given several examples, imagining that a skilled actor can perform all the physical reactions of pain, but there is no pain at all in his heart. Also imagine a resolute soldier who, even though he feels severe pain, is completely invisible in appearance. Since pain and associated bodily responses do not necessarily occur together, pain is clearly not a behavioral response of the body, so behaviorism is problematic.

The theory of mind-brain identity reduces mental attributes to brain nerve attributes, equates mind with brain nerve activity, and psychological events are brain nerve events. This position does not deny the existence of the above-mentioned psychological processes and mental states. These are events with mental attributes. For example, "Zhang San feels pain" means that Zhang San has the mental attribute of "feeling pain". However, it is further emphasized that all of these mental attributes can be reduced to certain cranial nerve attributes. For example, "feeling pain" can be equivalent to "activating a certain c-fiber of a cranial nerve". Since the attributes of the mind are the attributes of the brain nerves, and the brain nerves can produce causal power on the body, of course the mind also has causal power, and the problem of mind-matter causation is thus solved.

Some philosophers pointed out that the mind-brain identity theory cannot solve the problem: the mind has multiple realizability. Mental properties can be realized by different physical properties, so the mental property class is not equivalent to the human brain neural property class. For example, pain may not only be realized by the activity of a certain c-fiber cranial nerve group in humans, but may also be realized by the cranial nerves of other species that are very different from human cranial nerves, such as octopuses. Therefore, the mind-brain identity theory is not necessarily correct.

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Another possible branch of physicalism is eliminativism. Eliminativism does not reduce mental properties to any physical properties, but directly denies the existence of mental properties.

According to eliminativism, the commonsense psychological concepts that we are familiar with as mental attributes, including beliefs, desires, hopes, likes, doubts, judgments, worries, thoughts, feelings, experiences, and emotions, do not exist.

The reason why eliminativism denies common sense psychological theory is that it is a theory created by people to describe psychological phenomena before the development of neuroscience. Just like the myths and myths created by the ancients to explain natural phenomena, or the phlogiston and ether created by early science to explain natural phenomena, these ancient, outdated, wrong or inaccurate theories should be abandoned and replaced by replaced by more advanced scientific expressions.

Eliminativism also claims that the theories and concepts of common sense psychology are old, outdated, inaccurate and wrong, and that these theoretical concepts should be abandoned and replaced by neuroscience. The concepts of pain, happiness and sadness do not exist, only brain nerve activity exists. The obvious problem with eliminativism is that the relevant concepts and theories provided by common sense psychology are still the mainstream of cognitive science and psychology, and their explanatory and predictive power are still very good.

Reductive physicalism (behaviorism and mind-brain identity theory) seems to imply the tendency to master psychological knowledge by mastering physical knowledge. But this is not necessarily correct.

Imagine a genius scientist who has been wearing glasses since birth that only show black and white. He studied physics, biology, psychology, cognitive science and neuroscience, and mastered all the relevant scientific knowledge about the human brain seeing red. Although he had never seen red with his own eyes, when he took off his glasses At that moment, the bright red apple in his hand made him see red for the first time. At this time, he finally knew the color red and gained new knowledge about the color red. It can be seen that some psychological knowledge cannot be grasped by physical knowledge.

The above-mentioned behaviorism and mind-brain identity theory reduce mental attributes to some physical attributes. If behaviorism and mind-brain identity theory are abandoned and mental attributes are irreducible to physical attributes and mental attributes are essentially different from physical attributes, this is called anti-reductive physicalism.

If the two attributes are different, what is the nature of mental intelligence and how does it arise? To this, the functionalist answer is that the essence of mental attributes is functional states, which are a functional class implemented by physical systems. The emergentist answer is that mental properties are special properties of physical systems that emerge at the macro level but do not depend on the physical components or the way they are composed at the micro level.

The classic question posed by the British mathematician and computer scientist Alan Turing in his 1950 article "Computing Machinery and Intelligence" is "Can machines think?" and he proposed the Turing test. In the 1960s, the American philosopher Putnam advocated that the human heart is a Turing machine, and the brain is the hardware that executes the Turing machine.

Functionalism holds that mental properties are functional properties and mental states are functional states. For example, the psychological state of being in pain is a functional state that can be defined through input and output. The input can be defined as damage to body tissue, and the output can be defined as moaning, trying to press the painful area with your hand, believing that you are in pain, etc. These functional states can be realized in multiple ways. If a computer happens to be in the same defined "pain" functional state as a human being, then the computer is also in pain.

Different from the mind-brain identity theory, functionalism does not equate the state of pain with the state of the brain nerves or the circuit state of the computer that realizes pain. Just as computer software is different from hardware, and software must be implemented through hardware, functionalism advocates that psychological attributes are high-level attributes and are different from those brain nerves that realize high-level attributes.

In other words, the "mind" is a kind of "software" that can be huge, complex and incomprehensible, and the brain is the "hardware" that executes the "mind". There are hundreds of millions of neurons in the brain, and each neuron is in an activated or inactive state. Just like there are hundreds of millions of bytes on a computer's hard disk, each byte is in a 1 or 0 state. The brain, like a computer, also has areas responsible for working memory (cache) and areas for long-term memory (hard drive).

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Among the current trends in artificial intelligence, functionalism is perhaps the most popular theory of mind. If we can discover the software of the "mind", then we can realize the human heart on the computer. Artificial intelligence will likely have a heart, even consciousness, and may eventually be able to upload human hearts to computers.

However, functionalism also has many difficulties, and philosophers point out that the biggest difficulty is consciousness.

“Consciousness” here refers to a first-person subjective perspective experience. To help understand, American philosopher Nagel asked how to imagine what it is like to be a bat? Bats have no vision, but have powerful sonar capabilities, using the reflection of sound waves to move in the environment and find prey. In the first-person perspective of the bat, the surrounding environment and prey are constructed using sonar. It is difficult for us to imagine the first-person experience of being a bat, and it is difficult for bats to imagine the visual experience of being a human: the world is full of rich colors, clear outlines, dazzling sun, and deep darkness. This subjective perspective experience is consciousness, the difference between us being awake and fully asleep, the way the world appears to us.

Imagine being in the mental state of "seeing red." There may be another person who is also in this state at the same time, with the input of red visual experience, and the same output of believing that he sees red, saying it is red, etc., but what he experiences from his subjective perspective is green. We cannot tell whether what he is aware of is red, because he has called this color red since he was born, and his behavior is exactly the same as our input and output reactions to seeing red.

It is even conceivable that he may have no conscious experience, but his appearance is exactly the same as ours, and his behavior and speech expressions are completely normal. These thought experiments show that functionalists conceptually treat mental states as functional states defined by inputs and outputs, but that functional states cannot encompass consciousness.

In the first part of the novel "The Three-Body Problem" by science fiction writer Liu Cixin, it is described that an ancient civilization of three-dimensional aliens used a large number of soldiers to imitate the Turing machine's paper tape (the bits of the computer), and the civil servants were responsible for recording the results (state temporary storage) processor), jointly execute a pre-written rule instruction (software). The civilization in the novel attempts to use this method to implement the operation of a computer (called a human-column computer), and use it to calculate the trajectory of the three-body movement of stars. If functionalism is correct, then the mind can be written as a set of command rules (software), and imagine increasing the number of soldiers to billions or tens of billions, and collectively executing the software of this "mind".

Although the calculation output of the entire humanoid computer may look like a person talking and thinking, and when the humanoid computer enters the "pain" state, it will also output "believe that it is in pain", "making a wailing sound" and "thinking". Ways to Stop the Pain" results and more.

A scene from the film "The Three-Body Problem". Image source: Artstation

The question is who feels the pain? Is it the pain that every soldier in the entire human column computer feels, or is it the civilian officers who feel the pain? Or were the soldiers manning the reading and writing heads in pain? It seems that functionalism cannot explain the problem of human consciousness.

Another problem is that the mind as described by functionalism is only a syntactic machine and not a semantic machine, but the mind can process semantics. Imagine a room with a person who knows absolutely no Chinese, lots of notebooks, and a rule book of instructions from the mind of a native Chinese speaker. People outside the room can pass the Chinese questions through the crack of the door to the people inside the room. The people inside the room analyze the note according to the rules of this book, and after performing Turing machine operations on the notebook, output a Chinese response and send it to the people outside the room. It seems that the person in the room is the reading and writing head of the Turing machine, and the book is the control rule table. The problem is that the person in the room doesn't understand Chinese, he just follows the rules of the book and operates in Chinese that he doesn't understand.

So in the picture described by functionalism, the mind is just a machine that operates the rules of grammar. However, the human mind understands the meaning of language, and human beings use the meaning and reference of language to point to external things and to identify the truth of sentences. This characteristic of the mind is called intentionality. The mind can be about or directed toward external things, but things cannot.

There are still many problems with functionalism, such as triviality (almost all physical systems can be said to be computations), the limitations of Turing machines (the mind has certain capabilities but machines do not), and the continuous versus discrete problem (computers are discrete, But the mind may not be), analogy and digital issues (computers are digital, but the mind may not be), embodied cognition (meaning that the mind and cognitive activities are composed of the brain, body and environment, but computers are limited to symbolic operations), etc. .

Anti-reduction physicalism also seems unable to solve the problem of mind-matter causation. If the cause and effect of the physical system is closed (meaning that if a physical event has a cause at time point t, then this physical event has a sufficient physical cause at time point t), and there is a supervenience relationship between mind and matter (meaning that when a physical event has a cause at time point t The mental attribute M is realized by an entity x at a certain time point t because There is already sufficient causation to cause mental and physical properties at the next moment, leaving no room for mental properties to generate causal power.

In other words, mental properties do not produce any causal power, but this conclusion violates the common-sense mind-matter causation mentioned at the beginning of this article. Logically, this will lead to several options. One is to admit that mental attributes are equal to physical attributes, that is, mind-brain identity theory, which has the advantage of retaining mind-matter causation; the other is to admit that mental attributes have no causal power, which is called epiphenomenalism. Epiphenomenalism holds that physical properties can causally cause mental properties, but mental properties have no causal power. Just as the movement of the body under light will causally cause changes in the shadow, although the shadow moves with the body, the shadow has no causal power over the movement of the body. By the same token, epiphenomenalism claims that our brain nerves can cause various psychological phenomena or consciousness. Although we feel that psychological phenomena or consciousness cause brain activity or body movement, the causal power produced by psychological phenomena or consciousness is an illusion. , like a shadow cast in the mind.

The above is a brief introduction to several mainstream theories of metaphysics in contemporary mind and cognitive science. But there also seem to be problems or flaws with philosophical work in these sciences.

First, philosophy is an extremely large subject with thousands of years of research history. Since the birth of science hundreds of years ago, influenced by the development of science and the continuous subdivision and investment of scientific research institutions, the division of labor in philosophical research has become increasingly refined, and the philosophical methodologies of different schools vary greatly.

A teaching researcher engaged in philosophy of mind and cognitive science research is often unable to take into account other areas of philosophy such as history of philosophy, ethics, theory of knowledge, philosophy of physics, and philosophy of mathematics. He can only focus on special topics in cognitive science. Philosophical issues, not to mention that this kind of research requires pre-mastered scientific knowledge.

The high degree of division of labor has narrowed the scope of research topics in the philosophy of science. Many scientists have little expectation for "major ideological changes" or "major breakthroughs full of big patterns" in philosophy.

Second, philosophical research is not experimental research after all. Philosophical workers mostly have a background in humanities and social science research and are not familiar with the frontier advances in empirical science. However, contemporary science is advancing rapidly, and it is already quite difficult to master just one subtle research direction in scientific disciplines. not easy.

Therefore, philosophers need to learn more about scientific knowledge, participate in scientific conferences, understand scientific experiments, interact and learn from scientists on the details of scientific research, not only conduct spiritual exchanges between science and humanities at the macro level, but also provide more beneficial insights in micro research. Hypotheses, criticisms, deductions, and demonstrations to promote the true integration and development of disciplines.

Third, the refined division of labor in philosophy has resulted in a very small number of scientific researchers specializing in the philosophy of science. In addition, different philosophical methodological schools are inconsistent, making different philosophical researchers have different philosophical perspectives and opinions on science, which often leaves people at a loss as to what to do indirectly. As a result, the vast majority of scientists have no understanding of the work of the philosophy of science, and their understanding is one-sided and fragmentary, or they only have partial knowledge of philosophy or the history of philosophy.

At the same time, work in the philosophy of science has many advantages and solves many problems.

First, philosophy is consistent with the specialized division of labor in science. As a mature discipline develops, as more manpower and material resources are invested, the scope of research becomes wider, deeper, and more difficult. Just like the efficient division of labor among various disciplines and research groups in contemporary science, as scientific knowledge continues to advance, scientific research can only gain space for publication in a highly competitive international environment by gradually investing a large amount of resources in subtle empirical issues.

Similarly, the philosophy of science breaks down theoretical and metaphysical issues in various scientific disciplines step by step, and the research issues are mainly rigorous, meticulous and sophisticated. This is not a trivial study of scientific philosophy, but an accumulation of knowledge starting from the study of small problems from point to point, and gradually forming a new and clear theoretical framework.

Secondly, philosophy of science can contribute to science and solve problems, including clarifying important scientific concepts, discovering and criticizing scientific theoretical assumptions, proposing testable and predictive new theories and reflecting on scientific and technological ethics.

For example, the modular theory of mind proposed by American philosopher Jerry Fodor in 1960 had a huge impact on the evolution from behaviorism to computationalism in cognitive science and psychology. Another example is that the American philosopher Daniel Dennett provided a new theoretical interpretation for the children's false belief task experiment in 1983, making an outstanding contribution with applied significance to cognitive science.

In immunology, philosophers have had a major influence on the self-non-self framework of immunity. In the life sciences, philosophers play an important role in a variety of topics, including evolutionary altruism, the debate on units of selection, the construction of the "tree of life", the dominance of microorganisms in the biosphere, the definition of genes, the examination of the concept of innateness, etc. Philosophy of science has of course also made outstanding contributions in the fields of physics, evolutionary game theory, brain-like intelligence and artificial intelligence.

This article starts from the study of the causal relationship between mind and body, introduces the gist of several mainstream theories of mind, points out the problems faced by these theories, emphasizes why the problem of consciousness is a gap that may be difficult to cross in relevant scientific research, and finally analyzes the philosophy of science Research how to help science solve current problems.

The fly in the ointment is that the author is not familiar with science and technology ethics and cannot summarize the moral and value reflections that science and technology ethics provides for science. As the scientist Mr. Qian Xuesen pointed out, "Philosophy without science is lame, and science without philosophy is blind." It is expected that in the future philosophy and science can learn from each other's strengths and contribute to the happiness and progress of all mankind.