"In more philosophical terms, qualia are properties of sensory
experiences."

"The importance of qualia in philosophy of mind comes largely from the
fact that they are often seen as posing a fundamental problem for
physicalism. Much of the debate over their existence, however, hinges
on the debate over the precise definition of the term, as various
philosophers emphasize or deny the existence of certain properties."

"According to physicalism, the language of physics is the universal
language of science and, consequently, any knowledge can be brought
back to the statements on the physical objects."

"Scientific perspectives
V.S. Ramachandran and William Hirstein have proposed three laws of
qualia, or "functional criteria that need to be fulfilled in order for
certain neural events to be associated with qualia" by philosophers of
the mind:

"Qualia are irrevocable and indubitable. You don't say 'maybe it is
red but I can visualize it as green if I want to'. An explicit neural
representation of red is created that invariably and automatically
'reports' this to higher brain centres.

"Once the representation is created, what can be done with it is open-
ended. You have the luxury of choice, e.g., if you have the percept of
an apple you can use it to tempt Adam, to keep the doctor away, bake a
pie, or even just to eat. Even though the representation at the input
level is immutable and automatic, the output is potentially infinite.
This isn't true for, say, a spinal reflex arc where the output is also
inevitable and automatic. Indeed, a paraplegic can even have an
erection and ejaculate without an orgasm.

"Short-term memory. The input invariably creates a representation that
persists in short-term memory — long enough to allow time for choice
of output. Without this component, again, you get just a reflex arc.

"Attention. Qualia and attention are closely linked. You need
attention to fulfil criterion number two; to choose. A study of
circuits involved in attention, therefore, will shed much light on the
riddle of qualia."