Quale. Plural: 'qualia'. A quale, such as red, is a quality considered as it appears
to consciousness rather than as science might define it. Qualia are like sense data,
but universal, not particular. Etymologically 'quale' is to 'quality' as 'quantum'
is to 'quantity'. Two associated problems concern 'absent qualia' (...might someone
have no experiences at all but live like a human while being a zombie?) , and 'inverted
qualia' (whenever we both see something we both call red, might you be having an
experience I would call green if I had it?).
(A.R. Lacey: A Dictionary of Philosophy, Routledge 1986)
The subjective qualities of conscious experience. Examples are the way sugar tastes,
the way vermilion looks, the way coffee smells, the way a cat's purr sounds, the
way it feels to stub your toe. Accounting for these features of mental states has
been one of the biggest obstacles to materialist solutions to the mind-body problem,
because it seems impossible to analyse the subjective character of these phenomena,
which are comprehensible only from the point of view of certain types of conscious
beings, in objective physical terms which are comprehensible to any rational individual
independently of his particular sensory faculties.
(Ted Honderich: The Oxford Companion to Philosophy, Oxford University Press 1995)
see also this online abstract, compiled by David Chalmers, on Consciousness and Qualia.
Since this topic is much too comprehensive to be dealt with at this place, I refer
to various books that introduce the concepts and implications of Quantum Physics.
Furthermore, I list a few Web resources that cover this topic: