Functionalism

Functionalism

The view that mental states are defined as the combination of inputs, mental states and outputs happening in sequence.

Multiple realisability

The same mental state can be realised by different physical structures, as long as they perform the same functional role.

Qualia

The subjective, first-person qualities of conscious experience. What it feels like to have a particular mental state.

Inverted qualia

The possibility that two individuals could have identical functional states but different subjective experiences.

Inverted qualia example

Two people are looking at a tree, and they both believe and see and say it is green. One person sees green and the other person is colour blind and sees what the other would actually call red. However, because both have always labelled that experience “green”, their behaviour and responses are identical even though their subjective experiences differ.

Inverted qualia challenge to functionalism

If two people can have the same functional organisation but different experiences, then mental states may involve more than functional roles.

China brain thought experiment

Every neuron in a brain is replaced by a person in China who follows instructions so that the whole system reproduces the same functional organisation as a human brain.

Functional duplicate with no mentality

If functionalism is correct, a system that reproduces the same functional organisation as a brain should have the same mental states and consciousness.

China brain challenge to functionalism

Many people think that the coordinated population of people in China as a whole would not literally feel pain or have experiences, even if it replicated the functional organisation of a brain. This suggests functional organisation alone may not be sufficient for consciousness.

Mary argument applied to functionalism

Mary knows all possible functional facts about colour perception, including every input, internal process, and behavioural output involved in seeing colour.

Mary gaining new knowledge

When Mary sees red for the first time, she appears to learn what the experience of red is like, even though she already knew all the functional information.

Mary challenge to functionalism

If Mary can know all functional facts but still learn something new about the experience, this suggests that functional descriptions do not fully capture qualia, so mental states may involve more than functional roles.