What is pain? Surely we all know the answer to this. Certainly, we know when we are in it. If, for instance, a clinician asks me to rate my pain on a scale of one to ten, I can reply intelligibly. But the question ‘How precise was that?’ is irrelevant, as there is no objective criterion against which to assess ‘accuracy’. If I rate my pain as a ‘seven’, this is a way of expressing unpleasant feelings or sensations, not an estimation of a ‘knowable’ mental state that can be inspected by others for accuracy.

But even if we can’t define pain precisely, isn’t there a medical authority who can? A good place to begin is with the definition of pain proffered by the International Association for the Study of Pain (IASP): ‘An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.’

This acknowledges that the relationship between ‘actual tissue damage’ and the experience of pain is not a simple or direct one. People can suffer tissue damage and yet feel no pain. Or they may experience pain that feels as if it arose from injury (it is ‘described in terms of tissue damage’), but there may be no diagnosable lesion. A complaint of pain presented in the clinic—along with associated disability behaviours—may not correlate with identifiable pathology or ‘tissue damage’.

Neither clinicians nor scientists are able to identify a mental state called ‘pain’, and a pain complaint (‘it hurts’) is more performative expression than description. The IASP taxonomy of pain comes close to the same conclusion by accepting that ‘all pain is subjective’. Not even the neuro-scientist talks about pain without recourse to an imprecise language in which people express and respond to unpleasant sensations and emotions.

Reflecting the clinical purposes of the IASP definition, it encompasses both the sensory and emotional aspects of pain, but it does not include, for example, ‘hurt feelings’. Nonetheless, we commonly describe grief, for instance, as a kind of pain. ‘Pain’ is a term in common parlance, and we should not ignore these messy, everyday uses of words; they are valid and philosophically interesting. If we want to understand pain, we need to heed Wittgenstein: ‘the meaning of a word is its use in the language’.

If you take time to help me and I offer you a gift in return ‘for your pains’, or if I apologise to you ‘for being a pain’, then I am observing certain customs of reciprocation. ‘Pain’, in these uses, implies more than just a subjective experience, be it impatience, annoyance, or bodily strain. It entails also a burden or obligation for which amends or compensation may be appropriate. When we suffer pain of any kind, it is likely to raise questions about what caused it, whose fault it was, and who has an obligation to provide care or relief. Moral and political questions are never far away when we suffer pain.

The word ‘pain’ derives from the Latin poena, meaning ‘penalty’ or ‘punishment’. Romance languages use versions of the Latin dolor to talk about pain. But the English ‘pain’ originally referred to punishment or penalty for an offence, as well as to unpleasant bodily sensations and mental or emotional suffering. We still use the phrase ‘on pain of death’ to refer to capital punishment. But, in the past, pain meant punishment, and lawful punishments frequently involved the deliberate infliction of bodily pain.

Thomas Hobbes, for example, writes of ‘pain’ as extra-legal punishment. He also lists ‘stripes, wounds, chains, and any other corporal pain’ among the lawful punishments. Pain and punishment were inseparable.

Today, the deliberate infliction of bodily pain—even if state-sanctioned—is treated as inherently wrong. Torture in particular is out-lawed. In those jurisdictions that still have capital punishment, great effort is made (not always successfully) to try to ensure that the extinguishment of life will inflict neither pain nor visible bodily injury, and hence the uses of sedatives followed by lethal injections.

The modern historical trend in lawful punishment has favoured the deprivation of liberty (imprisonment) over the termination of life and/or the infliction of bodily pain and injury. One of the benefits that Jeremy Bentham (1748–1832) saw in his design for an ideal prison or ‘Panopticon’, for instance, was to make irons unnecessary, and hence eliminate a cause of pain and torture.

Bentham’s principle of utility asserted that the best criterion on which to judge a law or policy is the net sum of the consequential pains and pleasures. This led to a careful description of pain in its various forms: sensory, emotional, and social. He distinguishes between pains of privation, of the senses (divided into nine types), of awkwardness, of enmity, of an ill name, of piety, of benevolence, of malevolence, of the memory, of the imagination, of expectation, and pains dependent on association. This is a broad, even holistic, appreciation of what ‘pain’ means. But his aim was to determine principles of morality, public policy, and law. He was not writing a medical treatise.

Beginning in the nineteenth century, significant developments in anaesthesia occurred. Today, we are fortunate to have ready access to pain-relief for minor complaints, and to local and general anaesthesia during surgery. One of the consequences of this beneficial development, however, has been a tendency to regard pain as a medical—rather than a moral, legal, or penal—issue. And while anaesthetic and pharmaceutical technologies have done a huge amount to relieve or prevent much human suffering, medical sciences have not been entirely successful in the hoped-for ‘conquest of pain’. Chronic pain, in particular, remains a significant medical challenge, as well as a source of economically and socially costly disability.

Christian doctrines have held that pain is a curse to be endured, or even that it may signify martyrdom and salvation, and therefore is to be welcomed. But today, it’s common to hear that a person ‘should not have to suffer pain’, especially if that person is a child or a person nearing the end of life. Cases have been made for the reform of professional codes of ethics, healthcare systems, human-rights covenants, laws, and even constitutions, aimed at, in the words of Martha Nussbaum, ‘the mitigation of the sort of pain that is not an enrichment of the soul or a deepening of self-knowledge’.

There has been a flourishing of interest in the cultural, social, and political factors that affect pain. The roles played by learning and by social and economic factors are now widely recognized in medical theory and clinical practice, especially in the case of chronic pain. And while it is no longer lawful in any civilized society to use the infliction of pain as a means of punishment, new associations between politics, law, and pain have emerged, raising new and complex questions. For example, is there a right to pain relief? If we can prevent or relieve pain, does that mean there’s a socio-legal obligation to do so? In turn, we also have real power-struggles over what ‘pain’ signifies, whose complaints of pain are ‘genuine’, and who should receive healthcare and compensation. Compensation authorities, healthcare insurers, and personal-injury litigators all have vested interests, and law reforms are frequently called for.

So, while we owe a lot to medical science for preventing and relieving many kinds of pain that are, again to quote Nussbaum, ‘not conducive to anything good’, we cannot leave the question of what pain is—or the meaning of ‘pain’—in the hands of medical-scientific authority alone. And indeed clinicians today are (wisely) trained to accept that pain is what the patient says it is. People are skilled (in words and actions) at expressing, disguising, minimizing, elaborating, and sometimes exaggerating how ‘it hurts’.

Pain and complaint of pain raise important philosophical, moral, and political questions. And while we tackle them, something we can all do is try to communicate more fully and empathetically about one another’s pain and suffering.