The problem was famously addressed by René Descartes in the 17th century, resulting in Cartesian dualism, and by pre-Aristotelian philosophers, in Avicennian philosophy, and in earlier Asian traditions. A variety of approaches have been proposed. Most are either dualist or monist. Dualism maintains a rigid distinction between the realms of mind and matter. Monism maintains that there is only one kind of stuff, and that mind and matter are both aspects of it.
Each of these categories itself contains numerous variants. The two main forms of dualism are substance dualism, which holds that the mind is formed of a distinct type of substance not governed by the laws of physics, and property dualism, which holds that the laws of physics are universally valid but cannot be used to explain the mind. The three main forms of monism are physicalism, which holds that the mind consists of matter organized in a particular way; idealism, which holds that only thought truly exists and matter is merely an illusion; and neutral monism, which holds that both mind and matter are aspects of a distinct essence that is itself identical to neither of them.
Several philosophical perspectives have been developed which reject the mind-body dichotomy. The historical materialism of Karl Marx and subsequent writers, itself a form of physicalism, held that consciousness was engendered by the material contingencies of one's environment. The most explicit rejection of the dichotomy is found in French Structuralism, and is a position that generally characterized post-war French philosophy. The absence of an empirically identifiable meeting point between the non-physical mind and its physical extension has proven problematic to dualism and many modern philosophers of mind maintain that the mind is not something separate from the body. These approaches have been particularly influential in the sciences, particularly in the fields of sociobiology, computer science, evolutionary psychology, and the neurosciences.
Mind–body interaction and mental causation
Philosophers David L. Robb and John H. Heil introduce mental causation in terms of the mind–body problem of interaction:
Mind-body interaction has a central place in our pretheoretic conception of agency... Indeed, mental causation often figures explicitly in formulations of the mind-body problem.... Some philosophers... insist that the very notion of psychological explanation turns on the intelligibility of mental causation. If your mind and its states, such as your beliefs and desires, were causally isolated from your bodily behavior, then what goes on in your mind could not explain what you do... If psychological explanation goes, so do the closely related notions of agency and moral responsibility... Clearly, a good deal rides on a satisfactory solution to the problem of mental causation [and] there is more than one way in which puzzles about the mind's “causal relevance” to behavior (and to the physical world more generally) can arise.
[René Descartes] set the agenda for subsequent discussions of the mind-body relation. According to Descartes, minds and bodies are distinct kinds of substance. Bodies, he held, are spatially extended substances, incapable of feeling or thought; minds, in contrast, are unextended, thinking, feeling substances... If minds and bodies are radically different kinds of substance, however, it is not easy to see how they could causally interact... Princess Elizabeth of Bohemia puts it forcefully to him in a 1643 letter...how the human soul can determine the movement of the animal spirits in the body so as to perform voluntary acts—being as it is merely a conscious substance. For the determination of movement seems always to come about from the moving body's being propelled—to depend on the kind of impulse it gets from what sets it in motion, or again, on the nature and shape of this latter thing's surface. Now the first two conditions involve contact, and the third involves that the impelling thing has extension; but you utterly exclude extension from your notion of soul, and contact seems to me incompatible with a thing's being immaterial...Elizabeth is expressing the prevailing mechanistic view as to how causation of bodies works... Causal relations countenanced by contemporary physics can take several forms, not all of which are of the push-pull variety.—David Robb and John Heil, "Mental Causation" in The Stanford Encyclopedia of Philosophy
In neuroscience much has been learned about correlations between brain activity and subjective, conscious experiences. Many suggest that neuroscience will ultimately explain consciousness: "...consciousness is a biological process that will eventually be explained in terms of molecular signaling pathways used by interacting populations of nerve cells..." However, this view has been criticized because consciousness has yet to be shown to be a process. and the "hard problem" of relating consciousness directly to brain activity remains elusive.
Cognitive science today gets increasingly interested in the embodiment of human perception, thinking, and action. Abstract information processing models are no longer accepted as satisfactory accounts of the human mind. Interest has shifted to interactions between the material human body and its surroundings and to the way in which such interactions shape the mind. Proponents of this approach have expressed the hope that it will ultimately dissolve the Cartesian divide between the immaterial mind and the material existence of human beings (Damasio, 1994; Gallagher, 2005). A topic that seems particularly promising for providing a bridge across the mind-body cleavage is the study of bodily actions, which are neither reflexive reactions to external stimuli nor indications of mental states, which have only arbitrary relationships to the motor features of the action (e.g., pressing a button for making a choice response). The shape, timing, and effects of such actions are inseparable from their meaning. One might say that they are loaded with mental content, which cannot be appreciated other than by studying their material features. Imitation, communicative gesturing, and tool use are examples of these kinds of actions.—Georg Goldenberg, "How the Mind Moves the Body: Lessons From Apraxia" in Oxford Handbook of Human Action
The neural correlates of consciousness "are the smallest set of brain mechanisms and events sufficient for some specific conscious feeling, as elemental as the color red or as complex as the sensual, mysterious, and primeval sensation evoked when looking at [a] jungle scene..." Neuroscientists use empirical approaches to discover neural correlates of subjective phenomena.
Neurobiology and neurophilosophy
A science of consciousness must explain the exact relationship between subjective conscious mental states and brain states formed by electrochemical interactions in the body, the so-called hard problem of consciousness. Neurophilosophy is the interdisciplinary study of neuroscience and philosophy of mind. In this pursuit, neurophilosophers, such as Patricia Churchland, Paul Churchland and Daniel Dennett, have focused primarily on the body rather than the mind. In this context, neuronal correlates may be viewed as causing consciousness, where consciousness can be thought of as an undefined property that depends upon this complex, adaptive, and highly interconnected biological system. However, it's unknown if discovering and characterizing neural correlates may eventually provide a theory of consciousness that can explain the first-person experience of these "systems", and determine whether other systems of equal complexity lack such features.
The massive parallelism of neural networks allows redundant populations of neurons to mediate the same or similar percepts. Nonetheless, it is assumed that every subjective state will have associated neural correlates, which can be manipulated to artificially inhibit or induce the subject's experience of that conscious state. The growing ability of neuroscientists to manipulate neurons using methods from molecular biology in combination with optical tools, was achieved by the development of behavioral and organic models that are amenable to large-scale genomic analysis and manipulation. Non-human analysis such as this, in combination with imaging of the human brain, have contributed to a robust and increasingly predictive theoretical framework.
Arousal and content
There are two common but distinct dimensions of the term consciousness, one involving arousal and states of consciousness and the other involving content of consciousness and conscious states. To be conscious of something, the brain must be in a relatively high state of arousal (sometimes called vigilance), whether awake or in REM sleep, and vividly experienced in dreams. Brain arousal level fluctuates in a circadian rhythm but these natural cycles may be influenced by lack of sleep, drugs and alcohol, physical exertion, etc. Arousal can be measured behaviorally by the signal amplitude required to trigger a given reaction (for example, the sound level that causes a subject to turn and look toward the source).High arousal states involve conscious states that feature specific perceptual content, planning and recollection or even fantasy. Clinicians use scoring systems such as the Glasgow Coma Scale to assess the level of arousal in patients with impaired states of consciousness such as the comatose state, the persistent vegetative state, and the minimally conscious state. Here, "state" refers to different amounts of externalized, physical consciousness: ranging from a total absence in coma, persistent vegetative state and general anesthesia, to a fluctuating, minimally conscious state, such as sleep walking and epileptic seizure.
Many nuclei with distinct chemical signatures in the thalamus, midbrain and pons must function for a subject to be in a sufficient state of brain arousal to experience anything at all. These nuclei therefore belong to the enabling factors for consciousness. Conversely it is likely that the specific content of any particular conscious sensation is mediated by particular neurons in the cortex and their associated satellite structures, including the amygdala, thalamus, claustrum and the basal ganglia.
The following is a very brief accounting of some contributions to the mind-body problem.
Plato (429–347 B.C.E.) argued that, as the body is from the material world, the soul is from the world of ideas and is thus immortal. He believed the soul was temporarily united with the body and would only be separated at death, when it would return to the world of Forms. Since the soul does not exist in time and space, as the body does, it can access universal truths.
'Forms'...exist outside of space and time and that are both the objects of knowledge and somehow the cause of whatever transpires in the physical world [...] the immortal soul, in a disembodied state prior to its incarceration in a body, viewed these Forms, a knowledge of which is then recalled by incarcerated souls through a laborious process.—Alan Silverman, Plato's Middle Period Metaphysics and Epistemology
For Plato, ideas (or Forms) are the true reality, and are experienced by the soul. The body is for Plato empty in that it can not access the abstract reality of the world; it can only experience shadows. This is determined by Plato's essentially rationalistic epistemology.
For Aristotle (384–322 BC) mind is a faculty of the soul. Regarding the soul, he said:
- “It is not necessary to ask whether soul and body are one, just as it is not necessary to ask whether the wax and its shape are one, nor generally whether the matter of each thing and that of which it is the matter are one. For even if one and being are spoken of in several ways, what is properly so spoken of is the actuality” (De Anima ii 1, 412b6–9)
In sum, Aristotle saw the relation between soul and body as uncomplicated, in the same way that it is uncomplicated that a cubical shape is a property of a toy building block. The soul is a property exhibited by the body, one among many. Moreover, Aristotle proposed that when the body perishes, so does the soul, just as the shape of a building block disappears with destruction of the block.
My view is that this gland is the principal seat of the soul, and the place in which all our thoughts are formed.—René Descartes, Treatise of man
[The] mechanism of our body is so constructed that simply by this gland's being moved in any way by the soul or by any other cause, it drives the surrounding spirits towards the pores of the brain, which direct them through the nerves to the muscles; and in this way the gland makes the spirits move the limbs.—René Descartes, Passions of the soul
His posited relation between mind and body is called Cartesian dualism or substance dualism. He held that mind was distinct from matter, but could influence matter. How such an interaction could be exerted remains a contentious issue.
For Kant (1724–1804) beyond mind and matter there exists a world of a priori forms, some of which, space and time being examples, are pre-programmed in the brain.
...whatever it is that impinges on us from the mind-independent world does not come located in a spatial or a temporal matrix,...The mind has two pure forms of intuition built into it to allow it to... organize this 'manifold of raw intuition'.—Andrew Brook , Kant's view of the mind and consciousness of self: Transcendental aesthetic
Kant views the mind-body interaction as taking place through forces that may be of different kinds for mind and body.
On the epiphenomenalist view, mental events play no causal role. Huxley, who held the view, compared mental events to a steam whistle that contributes nothing to the work of a locomotive.—William Robinson, Epiphenomenalism
For Popper (1902-1994) there are three aspects of the mind-body problem: the worlds of mind, matter, and of the creations of the mind, such as mathematics. In his view, the third-world creations of the mind could be interpreted by the second-world mind and used to affect the first-world of matter. An example might be radio, an example of the interpretation of the third-world (Maxwell's electromagnetic theory) by the second-world mind to suggest modifications of the external first world.
The body-mind problem is the question of whether and how our thought processes in World 2 are bound up with brain events in World 1. ...I would argue that the first and oldest of these attempted solutions is the only one that deserves to be taken seriously [namely]: World 2 and World 1 interact, so that when someone reads a book or listens to a lecture, brain events occur that act upon the World 2 of the reader's or listener's thoughts; and conversely, when a mathematician follows a proof, his World 2 acts upon his brain and thus upon World 1. This, then, is the thesis of body-mind interaction.—Karl Popper, Notes of a realist on the body-mind problem
According to Searle then, there is no more a mind-body problem than there is a macro-micro economics problem. They are different levels of description of the same set of phenomena. [...] But Searle is careful to maintain that the mental – the domain of qualitative experience and understanding – is autonomous and has no counterpart on the microlevel; any redescription of these macroscopic features amounts to a kind of evisceration, ...—Joshua Rust, John Searle
- Chinese room
- Cognitive closure (philosophy)
- Cognitive neuroscience
- Consciousness in animals
- Descartes' Error
- Dualism (philosophy of mind)
- Embodied cognition
- Explanatory gap
- Free will
- Ghost in the Machine
- Hard problem of consciousness
- Namarupa (Buddhist concept)
- Neural correlates of consciousness
- Neuroscience of free will
- Philosophical zombie
- Philosophy of artificial intelligence
- Philosophy of mind
- Problem of mental causation
- Problem of other minds
- Quantum mind–body problem
- Sacred–profane dichotomy
- Strange loop (self-reflective thoughts)
- Subject–object problem
- The Mind's I (book on the subject)
- Turing test
Notes and citations
- Turner, Bryan S. Body and Society: Exploration in social theory 1996
- Kim, J., "Mind–Body Problem", Oxford Companion to Philosophy. Ted Honderich (ed.). Oxford:Oxford University Press. 1995.
- : Consciousness Studies
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