The Modal Structure of Phenomenal Experience

The next meeting of the seminar „Philosophy of Cognitive Science” will take place on December, 8th, at 10:30 (AM Warsaw, CET). Our guest will be Alistair Isaac (The University of Edinburgh). We will discuss the manuscript: The Modal Structure of Phenomenal Experience, which is the sixth chapter of his forthcoming monograph on phenomenal experience & measurement. To make the chapter easier (or possible) to understand, we’ve also attached a brief introduction to the book. 

Abstract: I claim that psychophysics produces models of phenomenal experience. These models are properly understood as the results of successful measurement, consequently scientific naturalists should be realists about them. The measurement practices of psychophysics that produce these models are evidentially autonomous—in particular, they do not rely constitutively on any assumptions about how psychophysics relates to neuroscience, or indeed to any other area of the sciences. The upshot of this autonomy is that the ontological status of these models is secured by the measurement practices that produce them, and does not require they be reduced to, or explained in terms of any more fundamental or physical stuff. By implication, physicalism places an extra-scientific demand on ontology that is inconsistent with the commitments of scientific naturalism.

The task of the present chapter is to defend the status of psychophysical models as the outcomes of successful measurement and as genuinely models of phenomenal experience, rather than mere summaries of behavior or indirect measures of neural activity. Before launching into that defense, it will be helpful to have some examples on the table.

Workshop will take place at  GoogleMeet (for link ask:

Introduction to “The Modal Structure of Phenomenal Experience” for Seminar 8.12.2022

Alistair Isaac

This is the 6th chapter of a monograph in progress. These notes are intended to fill in context and background to make the chapter accessible as a stand alone text. Drafts of the previous 5 chapters are available upon request.

  • The central argument of the monograph is as follows:
  • If we can measure x successfully, then x is real.
  • We can measure phenomenal experience successfully.
  • Therefore, phenomenal experience is real.

Real is understood here naturalistically, i.e. as the claim that those adopting the scientific worldview should accept any objects or properties successfully measured into their primitive ontology. If x is real in this sense, then there is no pressure or motivation coming from within scientific practice to reduce, eliminate, or otherwise “explain away” x. The conclusion that phenomenal experience is real is novel insofar as the standard naturalistic view within philosophy of mind is that phenomenal qualities are metaphysically suspect, and do require some kind of explanation, reduction, or elimination by the lights of the scientific worldview. One central aim of the monograph is to undermine this standard view.

I adopt a permissive view of measurement, on which measurement is simply a systematic procedure for representing objects or properties with numbers. This permissive view is not adequate for measurement to do any substantive epistemic work for science. I supplement this with the technical notion of successful measurement. A suite of measurement procedures is successful insofar as they exhibit improvement in three qualities over time:

  • 1. Stability — repeated measurement attempts deliver the same result (within the bounds of random error)
  • 2. Convergence — different measurement procedures, relying on different theoretical commitments, produce the same results (within the bounds of error)
  • 3. Precision — a measurement is precise to the extent that it exhibits small bounds on random error, i.e. repeated measurement outcomes fall close together

Successful measurement is a diachronic notion: no one measurement, and no state of measurement outcomes considered at a single point in time, counts as “successful.” Rather, a historical trajectory of evolving procedures that exhibit increases in stability, convergence, and precision over time is necessary for measurement success.

In Chapter 3, I use examples from fundamental physics, in particular the measurement of the fundamental physical constants, to argue that we should be realists about the outcomes of successful measurement. I take successful measurement outcomes to imply points of modally robust stability in the world independent of human interests or practices. These points stand in positions of relative distance to each other within a geometrical structure that we represent through physical scales (such as Kelvin, m/s2 , kg, or m3 kg-1 s-2 ). I call realism about these points and the structural relations that organize them geometrical realism. These points are modally robust in the sense that they are stable independent of the mode of access (this follows from convergence). Moreover, the stability (and reality) of these points does not presuppose that they can be directly realized in the contingent physical world. For instance, I discuss the example of high precision measurement of Boltzmann’s constant through acoustic gas thermometry, a method that assigns a high precision value to the “speed of sound in a vacuum” as a limit of the decreasing trajectory of speeds of sound through increasingly rarified noble gas. Here, a value which cannot be physically realized is nevertheless modally robust, accessible through successful measurement, and thus “real.”

Chapter 6 aims to demonstrate that psychophysical measurement is successful in this technical sense and that it targets phenomenal experience, rather than the neural or behavioral correlates of experience.


prothetic / metathetic — this is a distinction idiosyncratic to the psychophysicist S. S. Stevens — prothetic qualities are those that vary only in intensity (e.g. loudness, brightness), while metathetic qualities vary in quality (e.g. color, timbre).

jnd — just noticeable difference. Fechner’s argument that sensation could be measured relied on the assumption that all jnd’s are equal; Ch. 4 demonstrates that later psychophysical measurement procedures do not require this assumption.

Summary of previous chapters

Chapter 1 argues that naturalists should derive their ontology from measurement, as measurement practices remain stable across high-level theory change.

Chapter 2 introduces the permissive view of measurement.

Chapter 3 develops a transcendental argument from measurement success to geometrical realism: modally robust geometric structure between points of physical stability is a necessary condition for the possibility of successful measurement.

Chapter 4 introduces the basics of psychophysical measurement.

Chapter 5 concerns Multi-Dimensional Scaling and other dimension reduction techniques, arguing that (in some cases) the outputs of such procedures should properly be understood as part of the measurement process (rather than mere ex post facto data analysis). This point is important for understanding the epistemic status of models derived from MDS and in making a connection between psychophysics and psychometrics (which will be the topic of Chapter 7).

Drafts of all chapters are available upon request, please just contact me directly at

Phenomenal experience

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