I'm doing some research at the moment on pain, specifically physical pain. I'm particularly interested in types of pain and how pain can be pleasurable. The International Association for the Study of Pain has provided me with quite a neat starting point in terms of definitions.
This can be boiled down to three key points: whether pain is (as they state) by its very nature always unpleasant; that pain has a psychological and emotional aspect to it and that pain is also anticipatory. The latter is something that I had not previously considered, that the fear of pain is in and of itself, painful. Potential physical damage can hurt us and the anticipation of such is part of the experience of pain. This, of course, links in with the assertion that feeling pain is a two-part experience, occurring both in the mind and the body. We can only appreciate pain because we remember it and have an awareness of it. We feel it all the more when we expect it to happen, the body and mind prime each other for the delivery.
The way that the term is defined always stipulates pain as a negative, citing specifically that experiences which are not unpleasant should not be called painful. Given that pain has an emotional component and that it is always subjective, I think this is almost certainly a grey area. Whilst stating that one person's pain is another's pleasure might seem a little pat, the principle is sound. It's easy enough to appreciate that a balance of pain and pleasure during play is exciting and overall enjoyable, but enjoyment through pain itself is a contradiction that is fundamental to some aspects of BDSM, in particular ideas such as subspace. Under these definitons, such an experience would not be "painful".
Of course, these terms are medical and created for situations in which pain is a sign that something is wrong. This is not the angle that I am approaching it from, but these ideas are useful to contextualise my own explorations. To know that pain is something that you should not be experiencing, whilst actively seeking it out, is interesting in and of itself. To make pain pleasing, and to enjoy the anticipation of both these contrasting sensations: surely worth the wait?