Bohr’s complementarity

March 10, 2007 at 10:07 am (general philosophy)

A term coined by Danish physicist Neils Bohr applying to the two mutually exclusive ways of describing light (as a wave and (not “or”) as a particle). Consciousness, as well, seems to be describable under two mutually exclusive accounts: either through a 3rd person account (e.g. pain is a property caused by tissue damage and in turn causes words such as “ouch”) or a 1st person account (pain feels like this: [insert sensation]).

Some philosophers have abandoned attempts to reduce 3rd person accounts to 1st person or 1st person accounts to 3rd person. Instead, they invoke Bohr’s complementarity thesis as a metaphor to explain these mutually exclusive descriptions. Neither 1st or 3rd person accounts has an explanatory monopoly over the other, they argue. Both are true of consciousness.

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16 Comments

  1. zolk seth said,

    A term coined by Danish physicist Neils Bohr applying to the two mutually exclusive ways of describing light (as a wave and (not “or”) as a particle). Consciousness, as well, seems to be describable under two mutually exclusive accounts: either through a 3rd person account (e.g. pain is a property caused by tissue damage and in turn causes words such as “ouch”) or a 1st person account (pain feels like this: [insert sensation]).

    Some philosophers have abandoned attempts to reduce 3rd person accounts to 1st person or 1st person accounts to 3rd person. Instead, they invoke Bohr’s complementarity thesis as a metaphor to explain these mutually exclusive descriptions. Neither 1st or 3rd person accounts has an explanatory monopoly over the other, they argue. Both are true of consciousness.

  2. reformed nihilist said,

    I think the scism over 1st and 3rd person perpectives has plagued many areas of philosophy (not just the mind problem, but problems/psuedoproblems with truth and knowledge). The 1st person perspective is directly accessible, and certain on it’s own terms. However, we have found that cooperation and communication are valuable tools. In order to utilise these, we must find agreement and assume commonality. In order to reference this commonality within a large community, which is essential to our cooperation, we need to create a 3rd person. An abstract everyman, who represents a generalized commonality of belief. In 1st person I have no experience of China, but I am able to speak knowledgably about China in the third person if I have read numerous books, talked to many people, watched many progams about the subject. What we call scientific knowledge is abstractions and consistently coherent generalizations, that help us explain and predict future behaviour of our enviornment. The 3rd person is the abstract entity who possesses all scientific knowledge.

    These perspectives are only exclusive in a propositional sense, but clarity of language and meaning can solve this. “The sky is blue” is one proposition, and “I see the blueness of the sky” is another. Because language is social by nature, and most of our higher reasoning takes a communicative form (mathematical, propositional, etc.), propositions that speak in the 3rd person are weighed stronger.

    To summarize: Two heads are better than one, but once you add a third person, you are really getting somewhere.

    Edited by Reformed Nihilist on Jul 6, 2005 – 10:57 AM

  3. reformed nihilist said,

    I think the scism over 1st and 3rd person perpectives has plagued many areas of philosophy (not just the mind problem, but problems/psuedoproblems with truth and knowledge). The 1st person perspective is directly accessible, and certain on it’s own terms. However, we have found that cooperation and communication are valuable tools. In order to utilise these, we must find agreement and assume commonality. In order to reference this commonality within a large community, which is essential to our cooperation, we need to create a 3rd person. An abstract everyman, who represents a generalized commonality of belief. In 1st person I have no experience of China, but I am able to speak knowledgably about China in the third person if I have read numerous books, talked to many people, watched many progams about the subject. What we call scientific knowledge is abstractions and consistently coherent generalizations, that help us explain and predict future behaviour of our enviornment. The 3rd person is the abstract entity who possesses all scientific knowledge.

    These perspectives are only exclusive in a propositional sense, but clarity of language and meaning can solve this. “The sky is blue” is one proposition, and “I see the blueness of the sky” is another. Because language is social by nature, and most of our higher reasoning takes a communicative form (mathematical, propositional, etc.), propositions that speak in the 3rd person are weighed stronger.

    To summarize: Two heads are better than one, but once you add a third person, you are really getting somewhere.

  4. jaoman said,

    TecnoTut wrote:
    ”Some philosophers have abandoned attempts to reduce 3rd person accounts to 1st person or 1st person accounts to 3rd person. Instead, they invoke Bohr’s complementarity thesis as a metaphor to explain these mutually exclusive descriptions. Neither 1st or 3rd person accounts has an explanatory monopoly over the other, they argue. Both are true of consciousness”.

    Well, what can they do; after all, the dog ate their homework. Things fall, yet birds fly – this was something that was irresolvable once. Then we learned a little bit more about the nature of our environment, we learned how to think about it to account for all occurrences, and it made sense. Philosophers who have ceased looking for an explanation that will consistently fit the universe are simply not doing their job.

  5. ingrid said,

    Incidentally, Bohr’s principle (in part) has been shown false. (Photons were observed to display simultaneously wave and particle properties. The principle in part states that they are observed to be in one state or the other but not both simultaneously.)

    Anyway, I just take these two accounts to be different ways of speaking about mental properties. This doesn’t suggest that mental properties are both feelings and physiological properties.

  6. wonder kid said,

    i believe spinoza anticipated this approach to the so-called “mind-body problem” about three centuries before bohr offered his thesis, and dismissed the cartesian aporia thus:

    “the mind and the body are one and the same thing, which is conceived now under the attribute of thought, now under the attribute of extension.” (scholium to proposition 2 in Book III of the Ethics)

    two ways of talking about a person (pace strawson) — implications of an ontological nature, however, are unwarranted & unnecessary (pace occam).

  7. hamish macsporran said,

    To what extent is the analogy from complementary variables to mind-body doing any work:

    Are specific predictions about the nature of the relationship between mind and body being developed from this analogy?

    Is the mathematical formalism supposed to carry over from complementary variables to the mind body problem?

    If all philosophers are saying is that the mind and body are two ways of describing the same thing, then thats fine but it has little to do with QM and complementary variables.

    Complementarity (as exemplified by wave particle duality) within QM is not a concept that has aged well. Working physicists dont have much recourse to it any more (though no-one denies there are pairs of variables which cannot be simultaneously observed). It mainly rears its head in popular accounts.

    There are also some specific issues which do not make it an ideal analogy for the mind body problem:

    1. It is not possible to simultaneously carry out measurements of two complementary variables. I dont see why a neuroscientist could not be observing the brain of a subject from the 3rd person viewpoint, while the subject has experiences in the 1st person. Complementarity specifically rules this out.

    2. Although complementary variables are exclusive in the above measurement sense, they are generally relatable to each other in a mathematical sense. That is the mathematical relationship between two complementary variables can be understood by expressing the two bases in terms of linear operators in the same Hilbert space. It appears to me that ‘complementarity’ is being invoked specifically to avoid having to relate (reduce?) the 1st and 3rd person viewpoints.

  8. zolk seth said,

    HamishMacSporran wrote:

    I dont see why a neuroscientist could not be observing the brain of a subject from the 3rd person viewpoint, while the subject has experiences in the 1st person. Complementarity specifically rules this out.

  9. zolk seth said,

    That would be akin to saying that complementarity rules out person A seeing light as a particle and person B seeing it as a wave. But complementairty does not say that. Complementarity is used to explain how some entities can have different mutually exclusive properties.

  10. hamish macsporran said,

    Complementarity rules out the possibility that person A may make a meausrement of the particle properties of a photon (position) at the same time that person B makes a measurement of the wave properties (momentum) of the same photon.

    In addition, if person A makes a position measurement at time t and then at a later time t’ B makes a measurement of momentum then the earlier position measurement will have resulted in a wavefunction reduction, destroying the momentum information which the photon carried at that time. B can still make his measurement, but the results will essentially be random (ie maximally uncertain) if the position measurement was precise.

    The idea that entities may have different kinds of properties simultaneously is not exclusive to complementarity. A large red ball has the property of being large and being red simultaneously.

    Complementarity describes the fact that it is not be possible to gain knowledge of both of two complementary observables (I am deliberately avoiding the term property as I dont think the two are equivalent) for a single system, although either may be measured individually.

  11. hamish macsporran said,

    I agree that both folk-psychology and cognitive science have contributions to make to a science of mind and brain. However, I dont see why this relates to complementarity within QM. Complementarity has a very specific content which has little to do with simply claiming that one approach may supplement another.

    The vitamins I take supplement nutritionally the food I eat. Yet to claim that their relation can be understood in terms of quantum physics and complementarity would be ludicrous.

    Equally, to claim, for example, that the supplemental relation between thermodynamics and biology is analogous to complementarity is to misunderstand both complementarity and the relation between thermodynamics and biology. Bohr needed to develop the concept of complementarity because there was not a pre-existing concept that fitted the bill. Complementarity is quite definitely not a simple relation of supplementation.

  12. faustus said,

    Sheesh, I was just going to post here and Hamish, who is absolutely right, beat me to it.

  13. zolk seth said,

    HamishMacSporran wrote:

    Complementarity rules out the possibility that person A may make a meausrement of the particle properties of a photon (position) at the same time that person B makes a measurement of the wave properties (momentum) of the same photon.

    Which also implies that one person cannot see the photon as both a particle and a wave. And that is the point of the metaphor, is it not?

    The vitamins I take supplement nutritionally the food I eat. Yet to claim that their relation can be understood in terms of quantum physics and complementarity would be ludicrous.

    What I said is that there are two competing views of the mind and that perhaps both are true of the mind. So in that sense, one view supplements the other view. Furthermore, I said complementarity is a mere metaphor (i.e. a device that may illustrate a better understanding). I never said it is an actual formal theory in Folk-Psychology and cognitive science.

  14. hamish macsporran said,

    Is it?

    Does this imply that one person cannot have both the first person and third person view point simultaneously?

    It seems to me that rather than one viewpoint excluding the other (as they would if complementarity applied) they supplement each other, as you said.

    Any state of precise momentum can be expressed as a superposition of states with precise position. And vice versa. This is true of any complementary variables.

    Choosing one measurement basis over another is choosing a particular way of expressing the same information.

    In contrast it seems to me that the 1st person viewpoint contains stuff (qualia) that is not contained in the 3rd person.

  15. hamish macsporran said,

    Well, what I am asking is does the metaphor actually illustrate anything or lead to a better understanding? Is the metaphor any good?

    A good metaphor ought to take a complex and unfamiliar concept and relate it to a simpler more familiar idea. In this case we are trying to explain something that is familiar and simple (1st vs 3rd person) with something that is complex and unfamiliar (complementarity).

    Further, I dont think complementarity is even very like the supplemental relation between 1st and 3rd person. If the metaphor is supposed to lead to a better understanding, how will it do that if complementarity tells us nothing about the relation of 1st and 3rd person?

  16. zolk seth said,

    Rather than explaining the relation of mutually exlcusive properties/observables), I think the point of complementarity is merely to show that both view points are necessary for a better understanding of whatever natural phenomena that’s being invesitgated.

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