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MBTIT
- MBTIT claims that mental states are ontologically reducible to brain states
- So, mental states are identical to brain states in reality.
- However, this reduction is not analytic. Propositions about “mental states”
and propositions about “brain states” are not synonymous
- So, propositions about mental states cannot be translated into propositions
about brain states without loss of meaning
- There remains a conceptual gap between the two ways of describing the
same thing.
- This theory claims that there is type identity (ie a particular type of mental
state (A) is identical to a particular type of neural state (Y)).
- This means that all people who are in (A) are, ipso facto, in (Y) – this is a
denial of multiple realisability.
- We do not know all of these type identities with our current neuroscientific
knowledge
- These identities are known a posteriori - discovered through empirical
investigation rather than conceptual analysis.
- Analogous to how someone had to discover that H2O is identical to water in
reality, neuro-scientists need to discover the mapping of each mental state
onto a type of brain state
A dualist argument applied to MBTIT
- P1: If physicalism is true, having complete knowledge of all the physical facts
about colour perception would be to have complete knowledge of all the
mental facts involved in colour perception
, - P2: Mary has propositional knowledge of all the physical facts involved in
colour perception before her release
- “Mary is a brilliant scientist who…is forced to investigate the world
from a black and white room via a black and white television monitor”
- P3: When Mary sees colour (eg a red rose), she learns knew propositional
knowledge
- She learns the phenomenal fact of “what it is like” for both herself and
other people to see red
- She learns truths about qualia which are not deducible from physical
facts
- Qualia are intrinsic, phenomenal, non-intentional aspects of mental
states that are introspectively accessible
- P4: Mary learns a new fact so not all mental facts can be physical facts (since
Mary already knew all of these)
- C1: Therefore, there are non-physical facts about human colour vision
- P5: Non-physical facts are facts about non-physical phenomenal properties
- C2: Therefore, there are non-physical properties and physicalism is false
- P6: MBTIT is a physicalist theory and thus argues that everything is physical
or supervenes upon the physical
- C3: Therefore, MBTIT is false
The issue of multiple realisability
- The multiply realisable nature of mental states refers to the fact that the
same mental state can be realised by different brain states.
- Humans have different physiological brain structures (and therefore different
brain states) to mollusks
- We believe that mollusks experience a similar mental state of pain as we do
- So, each type of mental state is multiply realizable through more than one
distinct type of brain state.
- If each type of mental state is multiply realizable through more than one
distinct type of brain state, then any type of mental state cannot be identical
to any specific type of brain state.
, - Therefore, no type of mental state is identical to any specific type of brain
state.
- But MBTIT posits that the claim of type identity is that every type of mental
state has a corresponding type of brain state.
- So, if MBTIT is true, these two instances of 'pain' should only come from the
same or similar type of brain structure, but instead they come from two
vastly different physiological structures.
- So, the type identity claim made by MBTIT is false
Issue Dualist arguments against physicalism
Integration This objection attacks the truth of physicalism
Weighting This attacks the most fundamental presupposition which MBTIT
makes. If physicalism is false and dualism is true, then the rest of
the MBTIT analysis is redundant as not all language about mental
states can be reduced. Moreover, this objection does not merely
show that physicalism fails to offer sufficient proof or that
physicalism is unlikely - it proves physicalism false
So, this would be a fatal objection, if successful
Counter 1 A 'philosophical zombie'/a 'zombie' world is not conceivable. A
situation is conceivable if its description does not entail a
contradiction. A philosophical zombie is an exact physical duplicate
of a human being which nevertheless lacks any phenomenal
properties or qualia: it is ‘dead inside.’ Dennet argues that this
description does indeed yield internal contradictions. He claims that
consciousness is necessarily linked to our various capacities to act.
He draws an analogy between an act of stipulative imagination
removing consciousness, whilst leaving the cognitive system intact,
to removing health, while leaving all bodily functions intact. For
Dennett, consciousness is like health: it is constituted by the proper
functioning of the body and brain of a living human being. As long
as a human being is functioning appropriately physically, then,
necessarily, they will be healthy. Analogously, as long as a human
, being has their cognitive system intact, then, necessarily, they will
be conscious. A P-Zombie has their cognitive system intact but lacks
any phenomenal properties or qualia: it is ‘dead inside.’ But
according to Dennett this is logically impossible because their
cognitive system being intact ought to necessitate phenomenal
experience. So, P-Zombies are not conceivable. So, P-Zombies
cannot be used as evidence of property dualism
Integration This objection attacks the truth of P2 - that a P-Zombie is
conceivable
Success Physical properties (neurons, atoms, behavior) and phenomenal
properties (qualia) appear conceptually distinct. Because of this, we
can conceive of one without the other without them clashing.
Whereas, properties of a health (clear arteries, low resting heart
rate, functioning organs) and physical properties of the body (heart
rate, blood flow, insulin levels) are not so conceptually distinct.
Because of this, we cannot conceive of one without the other
without them clashing. So, the analogical form of the argument fails
as health and consciousness are not similar enough in the crucial
aspects. So, there is no contradiction within a P-Zombie. So, they are
conceivable
It appears undeniable that P-Zombies are at least conceivable. But
are they possible? Surely, just because the mind appears a certain
way in concept, that does not guarantee that it is or can be that
way?
Counter 2 Metaphysical possibility refers to the possibility that something
could exist in a possible world (as long as it is consistent with the
essential nature of reality) - even if it violates the actual physical
laws of our world. A situation is conceivable if its description does
not entail a contradiction. So, whether or not a state of affairs is
conceivable is determined by a priori reflection on the concepts
involved. For example, it is conceivable that water is not H2O
because the negation of “water is H2O” does not lead to a
self-contradiction. It is not logically contradictory to suppose that
water is, say, H3O instead. But whether or not a state of affairs is
metaphysically possible depends on the nature of the things
, involved. The nature of things is discovered a posteriori. For
example, we require sense experience to learn that water is H2O. A
posteriori discoveries can show that what is conceivable is
metaphysically impossible. So, for example, through sense
experience, we now know that “water being H3O” is something that
cannot exist in any possible world because it violates the essential
nature of reality. If a prior reasoning cannot guarantee metaphysical
actuality, then a gap between conceivability and possibility opens
up. Therefore, the conceivability of P-Zombies does not entail that
P-Zombies are metaphysically possible. So, despite that
conceivability, it may still be the case that mental properties (such as
qualia) are identical (or reducible) to physical properties.
Integration This objection is attacking the truth of P3 - that what is conceivable
is (metaphysically) possible
Success We can use a Cartesian response to try and save Chalmers. Our
conceptions only end up being metaphysically impossible if we
made those conceptions out of ignorance. Those who conceived of
the incomplete concept of water being H3O only conceived of the
impossible because they were ignorant to the true, essential
properties of water. This is not analogous to our conception of
P-Zombies. We have excellent knowledge of the essential
properties/reality of the human body (e.g C-fibers are essential
peripheral nerve fibers that detect and transmit raw "nociceptive"
signals (associated with a slow, dull, burning, or aching sensation))
and, through introspective evidence, we know about our the
essential properties/reality of our own phenomenal experience (e.g
we know what it is like to feel pain). So, we are epistemically justified
in deriving the metaphysical possibility of P-Zombies from their
conceivability (without ignorance). For example, from this
knowledge we can derive that it is metaphysically possible for
C-Fibers to fire without being accompanied by the phenomenal
experience of pain.
But are we sure our concept of the human body and mind is not
ignorant? Are we sure we have knowledge of the essential nature of
both physical and phenomenal properties? Neuroscience is teaching
us new facts about the human brain every day. Moreover, surely