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Metaphysics

  • Ontology: a theory of the nature of reality
  • Metaphysics: ontology + justifications for accepting that ontology as justified
  • What is the ontological difference between minds and brain?

Mind-body problem

  • Phineas Gage: our personality (thought to be non-physical) is actually directly affected by what happens to us physically.
  • Where does our mind reside?
  • Reductive physicalism: the view that the world is made only of physical stuff, including us.
  • Counterargument: thought experiment about Mary who study color yet see the color for the first time
    • The qualitative experience of seeing a color isn't the same as knowing facts about red.
    • Problem: begging the question
  • Qualia: instances of subjective, first person experience (what physicalism miss)
  • Substance dualism: the world is made of both physical stuff and mental stuff. Minds cannot be reduced to physical stuff.
  • Interactionism: the theory that there are two entities, mind and body, each of which can have an effect on the other.
  • How can a purely mental thing have any effect on a purely physical thing?
  • Mind-body problem: How can my body have a separate entity called a mind lurking inside of it - controlling it, and being controlled by it?
  • Not everybody falls cleanly into either the physicalist or the dualist camp.
  • Epiphenomenalism: physical states can give rise to mental states, but mental states can’t affect physical states.
  • Mysterianism: the question of consciousness is unsolvable by human minds.
  • Our brain is compartmentalized.
  • The way we understand our mind is through reflection. It’s deeply personal and subjective. But the way we understand our brains and bodies is objective and verifiable.
  • No amount of reflection could lead to any claims about neurons firing, and no amount of empirical research is going to give rise to what it’s like to see color through someone else’s eyes.
  • Both the mind-body problem and physicalism require our brain to do something they can’t do.

Rene Descartes: Dualism

  • “Official Doctrine”
  • Dualism: mind vs. body (in space, subject to mechanical laws)
  • The mind and body may be ontologically distinct, but they are inextricably bound in human beings. The mind is tethered to the body at the pineal gland.

Gilbert Ryle

  • “Conceptual analysis”
  • Descartes made a “category mistake” - mistakenly placing “mind” and “brain” in the same category of complex entities the “parts” of which can be specified as “causes” and “effects”
  • Mistake to place the mental states and events in this same “causal system” category as bodily states and events

Problem of other minds

  • epistemic asymmetry between the first-person and the second-or-third person
  • inverted spectrum

  • Solipsism

  • Descartes - Dualism

  • argue against global skepticism
  • 1） cogito, ergo sum. 自我认知的确定性 我思 除了思考和怀疑之外什么都推导不出来 如何能够跨越出去 为外部世界赋予真实性
  • 2） 对上帝存在的证明 如果上帝欺骗我的话 他就不是最完满的了 只要我的心灵能清楚明白地直观感知到的观念 都是上帝置入的

  • 3） 外部世界存在

  • Mill - 类比论证

  • 承认了笛卡尔的心物二元论，第一人称的心灵体验是直接的、不可怀疑的，第三人称的心灵体验是不直接的。
  • 类比论证：
    • P1: 我没法直接感知到他人的心灵
    • P2: 但我通过观察他人的身体行为的表现，发现他人的身体行为表现和我的身体行为的表现一样
    • C：那么我就可以推知，他人和我有一样的心灵体验。
  • 罗素将其总结为：
    • P1: 我有心灵状态A的时候总是伴随着身体状态B。
    • P2: 通过归纳得出：心灵和身体之间有因果关系。
    • C：我推测：当你出现身体状态B的时候，你有心灵状态A。
  • Counterargument：
    • This is merely an argument by analogy, which credibility depends not on logic, but on the similarity between two objects.
    • 对方完全有可能是一台制作精良的机器人，它行为表现上和我一样，但就是没有内心体验。从我心到他心的类比完全没有逻辑必然性。

  • Counter-counterargument:

    • 他心问题的症结就在于第一人称和第三人称的心灵感知的非对称性,不可能有逻辑上100%的正确答案
    • 最佳解释论证（Inference to the Best Explanation）
    • 奥卡姆剃刀（Ockham's Razor）

  • Ryle - 行为主义 Behaviorism

  • 只要承认心物二分的前提，那么他心问题就必然是一个死结。
  • 所有的错误都源于笛卡尔主义者非要执著于一个看不见摸不着的心灵实体。
    • 心身交互的难题：松果腺
  • 范畴误用（Category Mistake）：把心灵当成和物质同样的范畴的东西去描述
    • 心灵并不是一个实体，它只是一种假设，一旦把它当成一种实体，难免就会拿把它和物质实体当成是同一类的范畴，也就难免拿一些描述物质实体的词汇去描述所谓的心灵实体。
    • 他心问题就是范畴误用的后果。
  • 行为主义（Behaviorism）
    • “论迹不论心”：人们的内心是说不清楚的，我们须要说能够被测量的事情，即人的行为表现
    • 把所有的第一人称的心灵体验都翻译成第三人称的行为倾向
    • 心理学通用的范式
  • 心脑同一论（Mind-Brain Identity Theory）
    • 如果人外在的行为还是不能测量他的内心体验，那就检查脑神经的状况
    • 脑科学的通用范式
  • 行为主义和心脑同一论的底层的哲学理念是物理主义（Physicalism），将笛卡尔的心灵实体翻译成可测量的物理指标。二者都消解了心灵实体，从而也就消解了他心问题。

The Ontological Problem (by Paul Churchland)

  1. Dualism
    The essential nature of conscious intelligence resides in something nonphysical, in something forever beyond the scope of sciences.

  2. Substance Dualism

  3. Each mind is a distinct nonphysical thing, whose identity is independent of any physical body to which it may be temporarily ‘attached’.
  4. The characterization of the body is almost entirely negative.
  5. Descartes theorized the reality into two kinds:
  6. (1) res extensa - ordinary physical matter
    • It extend in space: any instance of it has length, breadth, and height, and occupies a determinate position in space
    • corporeal substance but it is something that only God can create

  7. (2) res cogitans - thinking substance

    • “There was one isolated corner of reality he thought could not be accounted for in terms of the mechanics of matter: the conscious reason of humankind.”
    • No spatial extension

  8. Property Dualism

  9. While there is no substance to be dealt with here beyond the physical brain, the brain has a special set of properties possessed by no other kind of physical object. It is these special properties that are nonphysical.

  10. Eg. having a sensation of red

    1. Epiphenomenalism
    2. Epi-: above
    3. physical states can give rise to mental states, but mental states can’t affect physical states.
    4. Our conscious mental states are little sparkles of shimmering light that dance over the wrinkled surface of the brain, but which have no causal effects on the brain in return.
    5. One’s actions are exhaustively determined by physical events within the brain, which events also cause the epiphenomena (desires, decisions, and volitions).
    6. There is therefore a constant conjunction between volitions and physical actions. But according to the epiphenomenalist, it is mere illusion that the former causes the latter.
    7. What can motivate such a strange view?

    8. Our neuroscientist can hardly deny that she has experiences, beliefs and desires. So they admit the mental properties but demote them to the status of causally impotent epiphenomena.

    9. Interactionist Property Dualism

    10. There are two entities, mind and body, each of which can have an effect on the other.
    11. The mental properties of the brain are an integrated part of the overall causal fray, in systematic interaction with the brain’s physical states and properties.
    12. One’s actions are held to be caused by one’s desires and volitions after all.
    13. Mental states and properties are irreducible.
    14. Mental states are held to be novel properties beyond prediction or explanation by the physical sciences.
    15. Mental properties are emergent properties, properties that do not appear at all until ordinary physical matter has managed to organize itself, through the evolutionary process, into a system of sufficient complexity.
    16. It sits poorly with the joint claim that mental properties emerge from nothing more than the organizational achievements of physical matter.
    17. If that is how mental properties are produced, then one would expect a physical account of them to be possible, even inevitable.
    18. The simultaneous claim of evolutionary emergence and irreducibility is prima facie puzzling, if not self-contradictory....

Arguments for Dualism

  1. Argument from religion
    1. Many religions are committed to the notion of an immortal soul.
  2. Argument from introspection
    1. When you center your attention on the contents of your consciousness, you do not clearly comprehend a neural network pulsing with electrochemical activity: rather, you apprehend a flux of thoughts, sensations, desires, and emotions.

  3. Argument from irreducibility

    1. There are abilities beyond the capacity of any purely physical system. (+qualia)
      1. our capacity to use language in a way that is relevant to changing circumstances
      2. our faculty of reason, particularly as it is displayed in our capacity for mathematical reasoning

  4. Reductive Materialism / Identity Theory

  5. Most straightforward

  6. Central claim: Mental states are physical states of the brain.

  7. Historical Parallels

    1. Sound \= compression waves. Warmth \= high average molecular KE.
    2. What we now think of as ‘mental states’ are identical with brain states in exactly the same way. This prediction has familiar parallels in our scientific history.

  8. Intertheoretic Reduction

    1. Intertheoretic identities: light is electromagnetic waves, temperature is mean molecular kinetic energy.
    2. If the new framework is better than the old at explaining and predicting phenomena, then we have reason to believe that the theoretical terms of the new theory are the terms that describe reality correctly.
    3. new framework \= neuroscience; to replace the old framework \= our common-sense conceptual framework for mental states

  9. Arguments for the identity theory
    Conclusion: the correct account of human-behavior-and-its-causes must reside in the physical neurosciences. Four reasons:

    1. Humans have purely physical origins and the ostensibly physical constitution of each individual human.
    2. The origins of animals appear to be exhaustively physical in nature → evolutionary history
    3. The neural dependence of all known mental phenomena
    4. The growing success of the neurosciences in unraveling the nervous systems of many creatures and in explaining their behavioral capacities and deficits in terms of the structures discovered

  10. Arguments against the identity theory

    1. Introspection reveals a domain of thoughts, sensations, and emotions, not a domain of electrochemical impulses in a neural network. Introspection cannot reveal microphysical details.
    2. “Category errors”: identification of mental states with brain states is a category error.
    3. “Leibniz’ Law”: two items, a and b, are numerically identical (i.e., a \= b) if and only if any property had by either one of them is also had by the other. → a way of refuting the identity theory: find some property that is true of brain states, but not of mental states (or vice versa), and the theory would explode.
    4. Mental phenomena have semantic properties (properties associated with their meaning) that brain phenomena don’t have
  11. e.g. a “belief” always has an object that is “believed” and a “desire” always has an object that is “desired.”
  12. This is apparently not true of brain phenomena
  13. e.g. neurons firing in the hippocampus don’t have an “object of their firing.”
  14. So, the argument goes, how could a brain state be identical to the mental state of desire?

Thomas Nagel

  • Few modern science examples shed light on the relation of mind to brain.
  • The subjective character of experience is very poorly understood.
  • We must consider whether any method will permit us to extrapolate to the inner life of the bat from our own case, and if not, what alternative methods there may be for understanding the notion.
  • If I try to imagine this, I am restricted to the resources of my own mind, and those resources are inadequate to the task.
  • If the facts of experience are accessible only from one point of view, then it is a mystery how the true character of experiences could be revealed in the physical operation of that organism.
  • Certainly it appears unlikely that we will get closer to the real nature of human experience by leaving behind the particularity of our human point of view and striving for a description in terms accessible to beings that could not imagine what it was like to be us.
  • Result: we can devise a new method - an objective phenomenology not dependent on empathy or the imagination.
  • Goal: describe the subjective character of experiences in a form comprehensible to beings incapable of having those experiences.
  • Phenomenology: raw experiences of those things that are included in what psychologists refer to as "conscious awareness”
  • immediately presented (rather than interpreted) mental experiences: sensory perceptions, pains, hopes, desires, doubts, mental calculations, etc.
  • introspective experience: being aware that he or she has the aforementioned experiences or engages in the aforementioned mental acts.
  • The mental phenomena we experience directly + our second-order sense of being aware that mental events happen \= knowledge of what it is like to be us

David Chalmers

The easy problems and the hard problems

  • The easy problems: phenomena associated with the notion of consciousness
  • an appropriate cognitive / neurophysiological model can clearly do the explanatory work
  • The hard problems: problem of experience
  • Subjective aspect
  • Why should physical processing give rise to a rich inner life at all?