The ‘Pilot-Wave’ Approach Viewed Through Systemic Functional Linguistics

Penrose (2004: 811):

… the de Broglie–Bohm ‘pilot-wave’ viewpoint (e) appears to have the clearest ontology among all those which do not actually alter the predictions of quantum theory. Yet, it does not, in my opinion, really address the measurement paradox in a clearly more satisfactory way than the others do. As I see it, (e) may indeed gain conceptual benefit from its two levels of reality — having a firmer ‘particle’ level of the reality of the configuration of the system, as well as a secondary ‘wave’ level of reality, defined by the wavefunction ψ, whose role is to guide the behaviour of the firmer level. But it is not clear to me how we can be sure, in any situation of actual experiment, which level we should be appealing to.

My difficulty is that there is no parameter defining which systems are, in an appropriate sense, ‘big’, so that they accord with a more classical ‘particle-like’ or ‘configuration-like’ pictures, and which systems are ‘small’, so that the ‘wavefunction-like’ behaviour becomes important (and this criticism applies also to (d) ). We know that quantum behaviour can stretch over distances of tens of kilometres at least, so that it is not just physical distance that tells us when a system ceases to look quantum mechanical and begins to behave like a classical entity. But nevertheless there is a sense in which a large object (like a cat) seems not to accord with the small-scale unitary quantum laws. …

But whether or not one believes that any particular such measure is appropriate, it seems to me that some measure of scale is indeed needed, for defining when classical-like behaviour begins to take over from small-scale quantum activity. In common with the other quantum ontologies in which no measurable deviations from standard quantum mechanics is expected, the point of view (e) does not possess such a scale measure, so I do not see that it can adequately address the paradox of Schrödinger’s cat.

Blogger Comments:

From the perspective of Systemic Functional Linguistic Theory, the two levels of reality in the de Broglie–Bohm ‘pilot-wave’ viewpoint are the two poles of instantiation: potential and instance. The secondary 'wave' level of reality constitutes the range of potential construals of experience as meaning, and the firmer 'particle' constitutes an instance of that potential: an actual construal of experience as meaning. So, since an actual experiment involves an actual construal of potential, 'we should be appealing to' both levels, instance and potential.

In this view, 'classical' phenomena, such as large-scale objects like cats, do accord with small-scale quantum laws, because an observation of a cat is an actual construal of experience of meaning: the most probable instance of potential construals. The improbability of other potential construals accounts for their non-instantiation at scales within the range of immediate human perception.

The thought experiment of Schrödinger's cat ceases to be a paradox when it is understood that 'classical-like' behaviour is an actual construal of experience as meaning, and that the notion of 'small-scale quantum activity' fails to distinguish between such a construal and the probabilistic potential construals of which it is an instance.