Contents Introduction Behaviorism Identity Theory Functionalism Causal Functionalism Mental Causation Consciousness Mental Content Physicalism Structural Identity Theory

Reductive and Nonreductive Physicalism Descartes combined substance & property dualism substance dualism: two distinct domains of substances body: extended matter mind: conscious thinkers property dualism: two mutually exclusive sets of properties physical properties: size, shape, etc. mental properties: thoughts & experiences Two types of physicalism reductive physicalism: identify mental properties with physical properties nonreductive physicalism: show how mental properties to be more loosely based on the physical supervene on the physical are realized in the physical What is Reduction Nagel reduction: "T2 is Nagel-reduced to T1 just in case all the laws of T2 are logically (and mathematically) derivable from the laws of T1 augmented with appropriate "bridge principles" connecting the expressions of T2 with expressions of T1."  (p.213) Example: Biochemical reduction of genetics. T2: Genetic theory including Mendel's laws of hereditary transmission of genes. T1: Biochemical theory including laws of chemical structure & behavior of DNA. Bridge laws: relating the proprietary vocabulary of the two theories genes are DNA molecules. Explanation: reduction effects logical derivation of the reduced theory from the reducing theory plus bridge laws. "This would in effect show T2 to be implicitly contained in T1 as a subtheory and not an independent theory concerning its [independent] domain." (p.213) The derivation not of T2 exactly as was but a corrected & improved version of T2 Microreduction -- of the laws governing higher level (macro) systems -- to the laws governing the behavior of their constituent parts are the rule (Putnam's picture) Psychology reduces to (brain) biology. Biology reduces to chemistry.. Chemistry reduces to molecular physics. Molecular physics reduces to atomic physics. Atomic physics reduces to subatomic physics. Payoffs: theoretical unification and systematization of overall scientific picture of the world correction and precisement of reduced theories explanation of why the higher level laws hold ontological simplification: fewer basic entities and properties assumed Arguments Against Mind-Body Reduction Doubts about the reducibility of psychology generally derive from doubts about the availability of appropriate psychophysical bridge laws. Biconditional laws of the form M<->P Subserve the ultimate goal of property identification: M=P Various theories of the mind represent so many proposals for bridge laws Behaviorism: bridge laws link mental properties to behavioral dispositions the reducing theory would be behavioristic psychology Identity theory: bridge laws link mental properties to neurophysiological properties the reducing theory would be neurophysiology Computational Functionalism bridge laws link mental properties to computational properties the reducing theory would be computer science Challenges to the reductionist program Davidson's psychophysical anomalism: denies the availability of psychophysical bridge laws. Multiple realization denies the availability of two-way biconditional laws of the form M<->P what are available are (open ended sets of) one-way conditional laws of the form P1->M P2->M P3->M . . . The disjunction strategy disjoin the various realizations yielding the biconditional law (P1 or P2 or . . . or Pn) <-> M objections to the disjunction strategy an open ended disjunction is not a proper disjunction disjoint properties -- e.g., being a shoe or a ship or sealing wax -- are bogus effect no genuine systematization or unification Supervenience Physicalism A tale of two "pictures" Cartesian dualistic picture: bifurcated reality a physical realm of bodies in space a mental realm of thoughts in consciousness Contemporary physicalistic picture: layered reality the world is a multilayered hierarchy of levels of entities with larger (macro) entities composed of smaller (micro) entities with the macrostructural states or processes being grounded in the microstructural states & processes The grounding relation: "higher level properties are in some sense dependent on, or determined by, . . . lower-level properties" (p.222) reduction: provides a very strong grounding two way M <-> P correlation tending toward property identification M = P supervenience: provides a weaker grounding one way P -> M determination leaving irreducible or "autonomous" higher level laws or regularities describing higher level regularities holding across various lower level realizations SP1: "Mental properties supervene on physical properties in that for every mental property M, if something has M, it has a physical property P such that necessarily if anything has P it has M." (p.223) necessarily requirement something stronger than mere correlation required for grounding correlations happily admitted by various nonphysicalist doctrines physicalism requires physical to mental determination SP2: "Mental properties supervene on physical properties in that if any x (in any possible world) and any y (in any possible world) have the same physical properties (in their respective worlds), then x and y have the same mental properties (in those worlds)." (p.224) Global supervenience If mental properties are wide -- if externalism is true then mental properties fail to supervene on locally on internal properties of subject who has them. nevertheless they may supervene globally on subject + environment GS: "Mental properties globally supervene on physical properties in that worlds that are physically indiscernible are also psychologically indiscernible; in fact, physically indiscernible worlds are one and the same world." (p.225) Emergentism "Emergentism . . . was the first systematic formulation of nonreductive physicalism as well as of the multilayered model of the world" (p.226) Defining doctrines Ontological physicalism: "All that exists in the space-time world are the basic particles recognized in physics and their aggregates." (p.227) Property emergence: "when aggregates of material particles attain an appropriate level of structural complexity ("relatedness"), genuinely novel properties emerge to characterize these structured systems." (p.227) resultant properties: are "additive" or "subtractive" i.e., predictable from the properties of the parts e.g., the mass of the table (= the sum of the masses of its parts) is "additive" emergent properties are "new" and "genuinely novel" i.e., not predictable from the properties of the parts e.g., the transparency of water what they were thinking: not additive: the transparency doesn't exist at the molecular level Kim's reservation: "perhaps it is possible to predict, on the basis of what we now know from solid-state physics, that lumps of H2O molecules will have the property" (p.227) Irreducibility of emergents: Emergent properties are irreducible to, and unpredictable from, the lower-level phenomena from which they emerge. (p.228) irreducibility doesn't hinge on the absence of psychophysical laws: emergentists claimed their were such laws predictability & unpredictability emergence is predictable in this sense: once it has been observed, further instances are predictable: having observed, in the first instance that C-fiber firings give rise to pain experiences we can predict that future C-fiber firings will give rise to pain experiences. emergence is unpredictable in this sense: the emergence was not predictable from the microprocesses in the first instance For reduction's sake, "from the emergentist's point of view, the bridge laws are precisely what need to be explained: Why do these mental-physical correlations hold?" (p.229) but these are inexplicable so emergent mental properties are irreducible The Problem of "Downward Causation" Downward causation: "once they have emerged, these higher-level properties begin to lead a life of their own, so to speak, and manifest their  powers by causally affecting lower-level phenomena." Implicit Argument If mental properties are real and irreducible (as emergentism says) they have irreducible causal powers They must effect either M -> M* causation or M -> P causation M -> M* causation causal realization principle: "If P1, P2, . . . are the realizers of Q, then to cause Q to be instantiated, you must cause one of the Ps to be instantiated." (p.231) M -> P causation incompleteness: missing realizer of M Supervenient causation story insufficiency of "supervenient causation" for irreducible causal powers of properties :. Mental properties are not real and irreducible (as emergentism says). Local Reductions and the Status of Mental Properties Structure restricted bridge laws: S -> (M <-> P) Kim's contention: Multiple realization 'in conjunction with the physical realization principle, guarantees that there are restricted bridge laws of this form" (p.234) Supporting consideration: "[R]elative to . . . types, the realizer P must be both necessary and sufficient for M, that is, the occurrence of M must be "controllable" by controlling the occurrence of P." (p.233) Supporting example: In building a realization of an abstract Turing machine "we should be able to guarantee the nonoccurrence as well as the occurrence of a computational state by manipulating its physical realizer." (p.233) Local Reduction: In S, M = P Kim concludes from the foregoing that multiple realization "entails the possibility of locally reducing psychological theories and states to physical/biological bases." (p.234) Objection: intraspecific multiple realizability especially for propositional attitudes (pace Davidson) Kim's reply: it's either reduction or elimination?! possibility of human psychology as a science depends on humans having "sufficiently similar neural realizers for their psychological states" (p.236) Qualia and Reductionism: A Dilemma Problem of qualia seem to be intrinsic to our experiences playing a functional role extrinsic: pain might be just the same as it is in itself & not cause wincing suppose the facial muscles are paralyzed pain wouldn't be the same as it is in itself it it felt different if this is right, qualia, not being identifiable with causal role occupants, are irreducible Dilemma: can't have your qualia and causality too if you avow the irreducibly qualitative nature of mentality you must disavow its causality if you avow the causality of mentality you must disavow its irreducibly qualitative nature