A Criticism of the IASP’s Definition of Pain Andrew Wright Abstract Like other fundamental experiences, the phenomenal qualities of pain seem to defy description. But unlike these experiences it is difficult to define pain in terms of a consistent relationship with the extra-mental world. The IASP’s solution is to qualify an imprecise characterisation of pain’s phenomenal qualities through an association with tissue damage and an ability to recognise pain sensation. In this paper I will argue that the IASP’s definition lacks the clarity and coherence necessary to provide an adequate definition of pain. I begin by setting out the difficulties of defining pain. I then describe the IASP’s solution and provide a detailed criticism of their approach. I also discuss inconsistencies evident in their wider taxonomy. In the final section I argue that pain can be objectively grounded by reference to pain’s evolutionary role and suggest an alternative definition. Introduction The difficulties associated with defining pain can be traced to the question of whether we can make meaningful statements about subjective experiences. There is no doubt that we are justified in responding positively to this question. There are, for example, characterisations of the phenomenal qualities of the visual experience of red and the sensation of touch which seem perfectly adequate for the purpose of defining these experiences. The question which naturally follows is what meaningful statements can be made about subjective experiences. The central issue here is that the phenomenal quality of a particular experience is only available to the subject who is having the experience. This issue gives rise to two problems which make the task of defining pain particularly difficult. The first problem is that in identical circumstances the phenomenal qualities of one individual’s experiences may not be like the phenomenal qualities of another individual’s experiences. For example, if my colour experiences are inverted in relation to your colour experiences, my experience of a ripe tomato would have the phenomenal qualities of green and yours would have the phenomenal quality of red. Neither of us would be aware that the phenomenal qualities of our visual experiences differed because we would both have learned that the relevant experience is ‘red’. So although ‘red’ refers to a fixed feature of the extra-mental world, it might refer to different phenomenal qualities. When it comes to defining phenomenal qualities this would not be an obstacle but for the second problem; the phenomenal qualities of experiences seem to be fundamental in the sense that they are not amenable to reductive description. There is something essential about the phenomenal qualities of red or pain, for example, which defies description in terms that are neither tautologous nor composed of synonyms. The solution to these problems is to accept that the phenomenal qualities of experiences cannot be defined by introspection of ‘what it is like’ to have these experiences. Instead, phenomenal qualities should be defined by reference to a consistent relationship with features of the extra-mental world. It is important that this relationship is consistent because inconsistency would lead to doubt about which