[I]t is an objective fact whether a certain experience is pleasurable or unpleasurable, and relatedly whether a particular conscious individual is presently experiencing something pleasurable or painful. It is an objective fact, so we may put it, about a subjective state.
Timothy Sprigge, ‘Is the esse of Intrinsic Value percipi?: Pleasure, Pain and Value’, in Anthony O’Hear (ed.), Philosophy, the Good, the True and the Beautiful, Cambridge, 2000, p. 123