This is my first post in a series highlighting current pain science that is relevant to philosophers writing about well-being and ethics. My work on this topic has been supported by the W. Maurice Young Centre for Applied Ethics, the Oxford Uehiro Centre for Practical Ethics, and the Wellcome Centre for Ethics and Humanities, as well as a generous grant from Effective Altruism Grants.

There have been numerous published cases in the scientific literature of patients who, for various reasons, report feeling pain but not finding the pain unpleasant. As Daniel Dennett noted in his seminal paper “Why You Can’t Make A Computer That Feels Pain,” these reports seem to be at odds with some of our most basic intuitions about pain, in particular the conjunction of our intuitions that ‘‘a pain is something we mind’’ and ‘‘we know when we are having a pain.’’ Dennett was discussing the effects of morphine, but similar dissociations have been reported in patients who undergo cingulotomies to treat terminal cancer pain and in extremely rare cases called “pain asymbolia” involving damage to the insula cortex.

It turns out there is a relatively tidy story that can be told about these cases recently revealed by neuroscience research. As pain signals ascend from the spinal cord to the brain, they split into at least two functionally distinct pathways. One pathway, called the sensory pain pathway, appears to be involved in the representation of the location of the pain, the intensity of the pain, and the modality of the pain (whether it is a “cutting pain” or a “burning pain,” etc.). The other pathway, the affective pathway, underlies how unpleasant we find the pain and how motivated we are to avoid it (there is a further distinction some make between primary and secondary affect that might also be relevant). As such, cases where people say they feel pain but are not bothered by it are cases where the sensory but not affective dimension of pain is active (note that this is not the same distinction, neuroanatomically, as that between “fast pain” and “slow pain”).

But important questions still remain about how best to characterise the affective dimension of pain. Does it involve a distinctive feeling? Is it simply an aversive desire that accompanies normal pain sensation? Or does it rather involve changes to our attentional processing or other aspects of our psychology? These questions are relevant for a number of different domains in philosophy.

Philosophers of mind and philosophers of cognitive science have paid the most attention to the affective features of pain. Many accounts of phenomenal consciousness have difficulty capturing the uniquely motivational and evaluative aspects of pain (and other bodily sensations such as itches). In particular, representationalist accounts of consciousness, which hold that differences in conscious experience always involve a difference in how the world is represented, at least initially seem to have trouble dealing with pain affect, since pain affect doesn’t seem to be representing the world as being different (in contrast to the sensory features of pain mentioned above). As a result, many philosophers of mind have put forward hypotheses of how best to capture the affective dimension of pain, ranging from a signal representing “aptness to harm” to an imperative command such as “move your hand away from the flame!” For highlights of these debates I highly recommend Murat Aydede’s SEP article as well as his book Pain: New Essays on Its Nature and the Methodology of Its Study.(as well as papers in the Bain, Brady, Corns volume I’ll mention below)

In the domain of practical ethics, it is of course extremely important to be able to characterise the unpleasantness of pain, since this aspect of pain is arguably what makes pain experiences intrinsically disvaluable (though of course there are other ways in which pain can be instrumentally disvaluable or valuable). One of the earliest references to the dissociation cases in the ethics literatures was R.M. Hare’s distinction between pain and suffering back in his 1972 paper “Pain and Evil.” More recently, in 2006, I wrote about the importance of understanding the affective dimension of pain for animal ethics in the journal Philosophical Psychology; it is, after all, the capacity for suffering that underlies many people’s moral concern for other animals. I later spent a year at the University of Western Ontario, where I applied these ideas to consideration of patients with disorders of consciousness in presentations to Adrian Owen’s lab group, the Canadian Association of Neuroscience, and the International Neuroethics Society (see here for a paper in AJOB that briefly summarises some of the points). The affective dimension of pain is also important in relation to the development of pain in foetuses and infants, and I’m fortunate to be at a place where I can work with neuroscientists on this important issue.

This dissociation is also important, I believe, for more fundamental debates in ethics. What exactly does the badness of pain consist in? Is it simply a sensation? Does it require an attitude of dislike? Or does it involve some type of motivation to avoid painful events? Numerous prominent ethicists, from Parfit to Korsgaard, have offered interpretations of the badness of pain that are based, in part, on discussions of the affective pain dissociation cases. David Bain’s recent article Why Take Painkillers? is a nice introduction to the issue.

So how, then, should we characterise cases where people report feeling pain but not minding it? Should we say that their pain sensation has changed? Or that the sensation remains the same but that they no longer dislike the pain? That they still dislike the pain but no longer have a desire to avoid it? Or that all of those things remain the same but that the person no longer attends to the pain as often?

I won’t attempt to answer the title question now, but I hope that the other posts in this series will provide information relevant to answering the question. My general view is that this is not a question that can be answered from the armchair: it is, in other words, not a question that philosophers can answer without engagement with other sciences. Here’s my conclusion from a paper that’s part of a valuable new edited collection on pain from David Bain, Michael Brady, and Jennifer Corns coming out in 2018:

Understanding pain is important for a number of philosophical projects. And the unpleasantness of pain is of particular importance. Though the science of pain has helped us to learn quite a bit about the unpleasant dimension of pain, we still lack crucial information needed to provide complete answers to questions in value theory, applied ethics, and the philosophy of mind. Given these limitations, the most important role philosophers can play is to collaborate with scientists to help nudge research towards answering some of these questions. Neither a pain science devoted exclusively to chasing clinically relevant results nor philosophers working primarily from intuitions can answer the most important questions about pain on their own. It is only though a collaboration that progress on the most important issues surrounding the unpleasantness of pain will occur. In what follows, I hope to more fully explain how pain science can be relevant for various philosophical questions.

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Adam Shriver is a Research Fellow at the Oxford Uehiro Centre for Practical Ethics and the Wellcome Centre for Ethics and Humanities.

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