The quality or nature of a given experience is often referred to by the term qualia, whose archetypical exemplar is "redness". For example, we might ask, "Is my experience of redness the same as yours?" While it is difficult to answer such a question in any concrete way, the concept of intersubjectivity is often used as a mechanism for understanding how it is that humans are able to empathise with one another's experiences, and indeed to engage in meaningful communication about them. The phenomenological formulation of "Being-in-the-World", where person and world are mutually constitutive, is central here.