identity theory of mind

identity theory of mind. Also known as type physicalism or central-state materialism, it is a position in the philosophy of mind asserting that mental states are identical to physical brain states. Developed primarily in the mid-20th century by thinkers such as Ullin Place, Herbert Feigl, and J. J. C. Smart, the theory emerged as a materialist response to Cartesian dualism and behaviorism. It proposes a direct ontological reduction, where types of mental events, like pain or the sensation of red, are strictly identical to types of neurophysiological events in the central nervous system.

Overview

The identity theory posits a strict one-to-one correspondence between mental state types and physical state types, arguing that discoveries in neuroscience will map sensations like thirst directly onto specific neural firings. Proponents like David Malet Armstrong further developed the theory by linking mental concepts to causal roles realized in the brain. This framework was articulated in seminal works such as Smart's "Sensations and Brain Processes" and Feigl's "The 'Mental' and the 'Physical'", positioning it as a cornerstone of reductive physicalism. Its rise was closely tied to the declining influence of Gilbert Ryle's logical behaviorism and advances in fields like neurophysiology.

Philosophical foundations

The theory is grounded in the principles of scientific realism and the unity of science, seeking to integrate psychology into the physical sciences. Key arguments include the appeal to Ockham's razor to avoid multiplying entities beyond necessity, as criticized in Rene Descartes' dualism, and the causal argument that mental states must be physical to interact with the physical world. Influential formulations were presented at institutions like the University of Adelaide and the University of Minnesota, where Feigl was affiliated. The logical structure of the identity claim was often analyzed through parallels with theoretical identifications in science, such as water being H2O or lightning being an electrical discharge.

Types of identity theory

Early formulations advocated **type identity**, insisting that every mental type corresponds to a single physical type, potentially universal across species. This faced challenges from the multiple realizability argument advanced by Hilary Putnam, which suggested a mental state like pain could be realized by different physical states in diverse organisms like humans, octopuses, or Martians. In response, **token identity** theories, such as those endorsed by Donald Davidson in his anomalous monism, argued that while each particular mental event token is identical to a physical event token, the types themselves are not reducible. Another variant, **central-state materialism**, specifically identified mental states with states of the central nervous system.

Relation to other theories

Identity theory directly opposed substance dualism as articulated by Descartes and property dualism, rejecting any non-physical mental substance. It was initially contrasted with behaviorism, as championed by B. F. Skinner and Ryle, by positing internal causal states. Later, it competed with functionalism, which defined mental states by their causal roles rather than their physical constitution, a view influenced by Putnam and Jerry Fodor. It also stands in tension with non-reductive physicalism and forms of property dualism like epiphenomenalism. Its materialist commitments align it with later developments like eliminative materialism proposed by Paul Churchland and Patricia Churchland.

Criticisms and objections

The most famous critique is Putnam's multiple realizability argument, which contends that identity theory is too restrictive given the diversity of physical systems that can instantiate mental states. Saul Kripke, in *Naming and Necessity*, presented a modal argument based on the necessity of identity, suggesting that the contingent link felt between brain states and pain sensations refutes their identity. The **knowledge argument**, exemplified by Frank Jackson's Mary's room thought experiment, claims physical information cannot capture qualitative experience or qualia. Others, like Thomas Nagel in "What Is It Like to Be a Bat?", argued for the irreducibility of subjective consciousness, challenging the theory's reductive aims.

Influence and legacy

Despite criticisms, identity theory profoundly shaped the landscape of the philosophy of mind, cementing physicalism as the dominant framework and influencing the development of cognitive science. It provided a crucial foundation for research programs in neuroscience and artificial intelligence, encouraging the search for neural correlates of consciousness. Its debates directly informed subsequent theories, including anomalous monism, biological naturalism, and various forms of non-reductive physicalism. The theory remains a vital historical position and a continuing reference point in discussions at centers like the Australian National University and in the works of philosophers such as David Chalmers and John Searle. Category:Philosophy of mind Category:Metaphysical theories Category:Physicalism