A pragmatic, general definition of pain

The current IASP definition of pain, including the proposed modification by Aydede,¹ is a good attempt at linguistically abstracting a purely subjective experience. Any such definition will necessarily be ambiguous (which, as Aydede points out, may be advantageous) but will also always be subject to counterexamples and exceptions. For instance, the experience of loud noise or bright light can fit the definition but still not be “painful” (ie, the experience may be unpleasant and distressing and be associated with actual or potential tissue damage, or paradigmatically result from actual or potential tissue damage, but not be actually “painful”). It is also the case that heavily damaged tissue may not produce pain; pain is most consistently associated with the process of tissue damage. Furthermore, there are those to whom pain is not unpleasant but may even be sought as a source of pleasure.

To even begin to define pain, we must concede that pain is a conscious, entirely subjective experience. To speak of pain in an unconscious (including a comatose) individual is nonsensical (and would render general anesthesia pointless as a means of eliminating the experience of pain). Consciousness is the essence of subjectivity; an individual's consciousness is inaccessible to all others.

The experience of pain thus falls in the same category as other subjective experiences, such as the color orange. So, how do we define the color orange? Pragmatically, we can say that orange is the visual color experience obtained when looking at a ripe tangerine. This definition avoids potential subjective pitfalls, such as the (unlikely) possibility that my visual experience of “orange” when viewing a ripe tangerine may be what you would call “purple” in your visual experience of looking at the same tangerine, or the possibility of a synesthete associating the color with a particular sound. In the case of colors, we are fortunate to know enough regarding the physics of light and vision to say that the visual experience of orange in a physiologically typical human can be generated by viewing wavelengths of light around 590 to 635 nm. This is a redefinition of the color orange in objective terms, but it does not alter the subjectivity of the conscious color sensation of “orange.”

In the case of pain, we have no readily quantifiable objective causal phenomena analogous to light wavelengths (more generally, electromagnetic spectra) in regard to color that we can use to redefine the multiple uses of the word “pain” in objective terms.

An alternative to the approach currently taken by the IASP and Aydede is to define pain in the pragmatic manner used for other subjective experiences, such as “smells like a rose,” “sounds like Paul McCartney,” or “feels like a gold nugget.” Defining pain in this manner suffers from the fact that the word, at least in English, is used to capture a wide variety of experiences, as well as being used metaphorically, but this problem is common to all attempts at defining pain. We can at least start with

“Pain corresponds to the sensory, perceptual, and emotional experiences of a physiologically typical individual when sensory innervated tissue of that individual is being damaged, or to similar sensory, perceptual, and emotional experiences when such damage is not actually occurring.”

To exclude those who find pain pleasurable, “unpleasant” could be added before “sensory” in the definition. The second part of the definition includes cases in which (1) tissue damage has already occurred, (2) there are stresses on the tissue of a type that could cause tissue damage, or (3) there are no objectively evident phenomena in the reported painful tissue causing the pain.

Disclosures

The author has no conflicts of interest to declare.