Type physicalism

The identity theory is one of the classic positions of the philosophy of mind. It is a naturalistic theory whose central thesis is that mental states are identical with neural states.

From behaviorism to the identity theory

The identity theory was formulated in the 1950s by Ullin Place and John Smart. The two philosophers went from two assumptions:

Place and smart contrast, present the hypothesis that consciousness or mental states, such as sensations are identical to brain states. This identity is therefore no question of the importance of mental terms as it was adopted in philosophical behaviorism, but simply an empirical discovery.

The systematic development of the theory of identity is an achievement of the 20th century. Even before Smart and Place it was discussed in the context of the Vienna Circle, it was conceived by Moritz Schlick and continued and clarified in the course of the 1950s, mainly by Feigl.

After the philosophical behaviorism had proved in the course of the 1950s and 1960s as practically and theoretically impossible, the identity theory was also extended further to Place and Smart beyond the narrow realm of consciousness and of sensations on the area of ​​propositional attitudes. Today, the identity theory is most often associated with the thesis that all mental states are identical with brain states.

The identity theory can be explained using simple examples - such as the identity of water and H2O. If we determine that water with H2O is identical, so we have the phenomenon of " water," explained scientifically. Similarly, if we have found that a mental state is identical with a brain state, we have the phenomenon of "mental state" explained scientifically. Note that water has a meaning other than H2O. Belongs to the importance of H2O about to be a molecule. On the importance of water not heard that. Nevertheless, one could say that water with H2O is identical. Two entities can be identical, without being identical in meaning. Similarly: expressions of mental states and brain states for expressions have different meanings, but can still refer to the same phenomenon, and thus denote Identical. This allows a materialist position beyond the philosophical behaviorism.

The identity theory was the most important position in the analytic philosophy of mind for a short time; she has this part of the field of philosophy in its present form significantly affected. By the late 1960s this concept was rejected by many philosophers again.

Objection to the identity theory

The identity theory was confronted from the beginning with many objections. Here are two called:

1) The identity theory was generally understood as a reductionist theory that wants to return the mental to the physical. However, identity is a symmetrical relation. Therefore, it was argued that the identity theory does not only materialize the mental, but also the material " spiritualize " the brain states would be awarded to mental properties.

For clarity, the above-mentioned Example, the identity of water and H2O are used. Water has to be liquid and transparent about the properties. When water and H2O but in reality are identical, so they must have the same characteristics: water is nothing but H2O. So also applies to H2O that it is liquid and transparent. Does this example also for the identity of mental state and brain state? Does it make sense, from a neural state to say that it is painful or stinging?

2) The decisive objection, however, refers to the multiple realization: A mental state can be realized in different beings throughout different brain states. So pain can not be identical to a particular brain state.

People can have pain, cats and (most likely) amphibians. But it is unlikely that all beings in the same neural state, when they are in pain. Too different are the brains. Let's call the neural states M ( in humans), K ( in the cat ), and L ( the Lurch ). Now, if the different neural states M, K and L realize all the pain, so pain may simply not be the same as one of these states.

From the identity theory to functionalism - and back?

In particular, the Objection of multiple realization contributed to a rapid loss of popularity of the identity theory. Hilary Putnam, who in 1967 brought the objection into play, also offered the same to an alternative: the functionalism. The different brain states should implement all a functional state which is then identical to the mental state. As an example, the blueprint of a clock can be used: The blueprint specifies functional states. The clock can then be constructed from various materials, which realize all the functional states. Functionalism was for the following decades to " orthodoxy " in the philosophy of mind.

Lately, however, come again increasingly voices calling for a return to identity theory. It should be noted that functionalism could not solve the problem of qualia. In addition, considerations of Jaegwon Kim for multiple realization play a big role here.