What is physicalism?


  • [Required] http://www.unc.edu/~ujanel/Materialism.htm
  • [Required] stanford:physicalism
  • Campbell, K. (1967) "Materialism," in The Encyclopedia of Philosophy, Paul Edwards (Editor in Chief), Volume 5: 179-189, New York: Macmillan Publishing Co. (New version: Keith Campbell (2006) "Materialism" Encyclopedia of Philosophy. Ed. Donald M. Borchert. Vol. 6. 2nd ed. Detroit: Macmillan Reference USA, 2006. p5-19. HKU has online version)

Some main positions

  1. Monism - there is only one kind of stuff in the world
    • Physicalism - everything is physical
    • Idealism - everything is mental
  2. Dualism - there are two independent kinds of stuff in the world
  3. Eliminativism - the mental does not really exist

Eliminativism vs physicalism

  • Compare: Qi (氣) does not exist vs. Qi is a kind of electromagnetic wave.

Two versions of physicalism

  1. Reductive physicalism = Everything can be reduced to the physical.
  2. Non-reductive physicalism = Everything supervenes on the physical even if they are not reducible to the physical.

Reduction (roughly) : x reduces to A B C = x can be defined in terms of A B C.

David Lewis on supervenience:

@A dot-matrix picture has global properties -- it is symmetrical, it is cluttered, and whatnot -- and yet all there is to the picture is dots and non-dots at each point of the matrix. The global properties are nothing but patterns in the dots. They supervene: no two pictures could differ in their global properties without differing, somewhere, in whether there is or there isn't a dot.@ Lewis, D. (1986) On the Plurality of Worlds, Oxford: Blackwell, p.14

Why opt for supervenience rather than reduction?

  1. Multiple realization - perhaps many configurations are sufficient for x. A B C, D E F, etc. No single physical definition of x available.
  2. A preference for emergentism - mental properties emerge out of physical ones but are not identical to them.

How do we define "physical"

Some proposed definitions of "x is physical"

  • x occupies space, x has a spatial location
  • x is a pattern of energy


  1. According to physicalism, "x is physical" is defined by "x exists according to physics".
  2. But "physics" just means "theories of physical things".
  3. So the definition of physicalism is circular.

Hempel's dilemma

  1. Either we define "physical" as "what exists according to the physics we have now", or it is defined as "what exists according to the final physics theory we have in the future".
  2. If we take the first option, then physicalism is false.
  3. If we take the second option, then physicalism is trivially true.


  • The third premise is false. We might not have an final physics, or our final physics might be false because of limitations of our knowledge.
  • Maybe we should not define what is physical in terms of any particular stage of physics, but in terms of our philosophical intuition.
  • A term can be meaningful even if it cannot be defined.

Appeal to composition

  • x is physical = x is made of the same stuff as [point to examples of paradigm cases of physical things]
  • Compare x is red = x is of a similar color as


  1. What if panpsychism is true?
  2. What if the human brain contains some unique physical stuff not found in [examples of paradigm cases of physical things]?

Physical as "non-mental"

@A fourth strategy, suggested by Campbell (1967), is to start with some paradigmatically mental properties, or (better) a list of all the known mental properties, and some paradigmatically physical ones, and then characterize dualism as bluntly separating the two at the level of fundamental entities: “Materialism” would be the claim that none of the world’s basic components has any of the mental properties; any subject of mental properties must be composed solely of basic elements that individually do not have them, and for anything that has a mental property, its doing so must consist entirely in an arrangement of the basic components.@

  • But what if the world does not have a fundamental level? what if matter is infinitely divisible? How can the proposal be modified?