Is absence of evidence of pain ever evidence of absence?

Deborah J Brown,Brian Key

doi:10.1007/s11229-020-02961-0

Abstract

Absence of evidence arguments are indispensable to comparative neurobiology. The absence in a given species of a homologous neural architecture strongly correlated with a type of conscious experience in humans should be able to be taken as a prima facie reason for concluding that the species in question does not have the capacity for that conscious experience. Absence of evidence reasoning is, however, widely disparaged for being both logically illicit and unscientific. This paper argues that these concerns are unwarranted. There is no logical barrier to formulating cogent absence of evidence arguments; indeed, accepting such arguments is part of what it is to be committed to falsifiability as a critical aspect of the scientific method. Absence of evidence arguments can always be blocked, however, by assuming that psychological properties are ‘multiply realizable’. While we take multiple realizability to be highly likely at some level of analysis, we argue that it is question-begging to assume that it exists at every level of analysis, and thus it should not automatically be thought to undermine absence of evidence reasoning in the animal consciousness debate. Using the example of pain and focusing on homologies at the level of information processing tasks, we show how, in the science of consciousness, an absence of evidence might well serve as evidence of absence.

Highlights

You are as certain as you can be that the stone paperweight on your desk does not feel pain even though you have no evidence of this
We focus our attention on pain for illustrative purposes but because pain is robustly coupled to emotion, motivation and behaviour in humans, and in comparative studies, invites arguments from analogy based on multiple criteria
Let us be clear about our intentions: We do not assume that the example we offer below of an absence of evidence argument—‘FISH’—is sound; only that it is a kind of argument that could be cogent if the right epistemic conditions were met

Summary

Introduction

You are as certain as you can be that the stone paperweight on your desk does not feel pain even though you have no evidence of this. It is argued first that motor behaviours do not necessarily indicate feeling states such as pain, and second, that defined neural circuitry is necessary for such states, and in its absence, there can be no pain These ideas, which we endorse, are closely linked to the well-established evolutionary and bioengineering principle that structuredetermines-function. It is counterargued that the absence of evidence for a certain kind of neural circuitry is not evidence of an absence of pain It exists and is somehow— unknown—multiply realized in different species. 1, we defend absence of evidence reasoning drawing on, among other things, results from informal logic These results delineate the kinds of epistemic contexts in which absence of evidence arguments can be cogent. The point of the exercise is to establish the acceptability of the form of the argument, not, on this occasion, its content

Absence of evidence arguments and the science of consciousness

Absence of evidence of neural circuitry in fish

Addressing multiple realizability at the correct level of abstraction

Beyond multiple realizability

Conclusion