PHYSICALISM (aka MATERIALISM)

There is no spirit, hence no non-physical "mind".

The only reality is physical (material).

In principle, everything that occurs can be explained in physical terms.

Advantages:

• There is no mind-body interaction problem (unlike Dualism).
• Our experience consists of single unified objects, instead of an infinitely varied series of sensations, because our diverse sensations are caused by single material objects (unlike Idealism).

THE PROBLEM FOR PHYSICALISM

If there is no such thing as mind, then to what do mental terms refer?

(Mental terms: mind, mental state, idea, thought, sensation, intent, hope, love, etc.)

Each physicalist theory is distinguished from other physicalist theories by the way it answers this question.

Philosophical Behaviorism

Every mental term refers to a disposition to behave in a particular observable manner under certain observable conditions.

Advantage:

• The truth or falsity of any statement using mental terms can be empirically determined.

Disadvantages:

• The inner aspect of our experience is left out.
• A truly comprehensive behaviorist definition of a mental term must make use of other mental terms, creating a vicious circle.

Identity Theory (Reductive Materialism)

Every mental term refers to a type of physical state of the human brain and nervous system. Mental states are actually brain states.

Advantage:

• Reduces the whole range of mental states to a single common denominator, a scientific description of brain activity.

Disadvantage (for Churchland):

• Faces hopeless task of matching vague psychological terminology to precise neuroscientific descriptions.

Functionalism

Every mental term refers to an internal state (of a complex mechanism) that has a particular functional role in a set of causal relations between external conditions, other internal states, and bodily behavior. A mental state is a particular way of processing input (e.g. sensory stimulation) such that a particular output (behavior) is the result.

Advantages:

• Definition of mental states is not specific to the human brain; opens up the possibility of artificial intelligence, i.e. inorganic machines that have mental states.
• Not biological, so psychology as a separate science is preserved.

Disadvantages:

• Definition of mental states not specific to the human brain (this is a problem if only brains can have mental states).
• Leaves the qualitative nature of experience out of the description of a mental state.
• Like Identity Theory, tied to our current psychological conceptual framework.

Eliminative Materialism

Every mental term is a vague and misleading reference to certain physical activities of the human brain and nervous system. In fact there are no such things as "mental states". The best way to understand ourselves is in strictly neurophysiological terms.

Advantage:

• No longer ties us to an unscientific psychological vocabulary.

Disadvantage:

• Giving up our psychological vocabulary is impractical, even in the long term.