Philosophy and the Brain

1. Philosophy and the Brain

2. Brain death • Organismal definition of death – irreversible functioning of the organism as a whole • Historical definition of death: loss of cardiopulmonary function (which usually led to irreversible brain damage within a short period of time) • However, advances in technology e.g. artificial respirators enable continuation of cardiopulmonary function even when the brain is dead • Determination of brain death • Three essential signs: • Irreversible coma (flat EEG) • Absence of brainstem reflexes (e.g. cough reflex, pupil contraction in response to light) • Apnea (cessation of breathing)

3. Brain death • Does brain death mean death? • If complete dependence on an external body (e.g. a respirator) for blood circulation and oxygenation is considered to be death, are foetuses dead? • Not all integrated functions of the body are dependent on the brain (e.g. growth, maintainance of homeostasis) • It is possible for brain-dead pregnant women to be artificially sustained for gestation of their foetuses • Alternative definitions of death • Cardiopulmonary failure • Death as a continuous process

4. Higher-order brain death • If parts of the brain involved in thought / analysis are destroyed but the brainstem remains intact, should the person be considered to be dead?

5. What is consciousness?

6. Brain-in-a-vat thought experiment • If the brain is indeed the seat of consciousness: • A brain is placed in a vat, receiving artificial stimulation identical to its natural electrical signals, it is not possible to tell, from the perspective of that brain, whether the things it perceives are actually true or merely false electrical signals • The Matrix

7. Mind-body problem • What is the relationship between mind and body? • Dualism: Mind and body are inherently separate • Monism: Mind and body are of the same substance • Physicalism: Both are of matter • Idealism: Both are of the mind

8. Dualism • The mind and body are fundamentally, completely distinct in nature • The body is like a machine, with material properties • Follows the laws of nature and is able to act on other physical objects • The mind is nonmaterial and does not follow the laws of nature • Ergo cogito sum: • One can doubt the actual existence of one’s body (brain-in-a-vat) but not the actual existence of one’s mind. • Proponent: René Descartes

9. Criticisms of dualism • If mind and body are made of fundamentally different substances, how can one affect the other? • I.e. how can the mind affect the physical body when it is itself non-physical? • Objection to Descartes’ mind-body dualism by Princess Elizabeth of Bohemia in 1643 • “I beseech you tell me how the soul of man (since it is but a thinking substance) can determine the spirits of the body to produce voluntary actions” • Similarly, how can our physical stimulation of sensory organs result in perception and sensation in the mind when the two are of different natures?

10. Physicalism (reductive) • Basic idea: Mental states are caused by physical states • Reductive physicalism • Reductionism – reducing complex systems to a sum of their parts • Reductive physicalism: Everything in the world can be analytically reduced to their fundamental physical or material basis • Applied to the mind-body problem: all mental states and processes can be reduced to physical states and processes • I.e. thoughts, feelings etc. can be reduced to, for e.g., neurons firing in the limbic system, amygdala and the relevant parts of the brain

11. Physicalism (non-reductive) • Non-reductive physicalism • Supervenience: The mind and body are at different levels of meaning; the mind supervenes on the body • “Pixels on a computer screen” • Mental states are caused by physical states but not necessarily reducible to them

12. Idealism • Esseestpercipi – to be is to be perceived • Material things do not exist outside of our perceptions of them • An object is merely a collection of ideas; for e.g., an apple is the term we give to a certain shape, smell, taste, colour and so on which tend to occur together • Notably, the physical world is empirical and based on our experience of it • Perception of physical objects is not caused by the observation of a physical object • I.e. we do not need physical objects to explain our ideas (refer to objection to Descartes)

13. Idealism • “If a tree falls in a forest and there is no one to hear it, does it make a sound?” • Idealism asserts that the tree does not exist if there is no one to perceive it, and it would thus be impossible for a nonexistent tree to fall • Trees popping in and out of existence? • Proponent: Bishop George Berkeley

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