Pleasure and pain are synonymous; we wouldn't be able to feel such great pleasure without the pain.

The universe is not perfect. Ideally, it would be like your later suggestion.

I'd struggle to answer this - "what" - maybe. "Why" requires pre universe information, that I have not acquired. Could I?

How can pleasure and pain be explained, why is damage to the body or satiation accompanied by a qualitative feeling rather than simply being perception together with functional stimulus and response? — Enrique

Currently, those percepts are "explained" by labeling them as "Consciousness", which explains nothing, or as "Neural Correlates", which also explains nothing. My thesis of Enformationism is an attempt to explain such perplexing topics from a cosmic perspective.

Unfortunately, in order to grasp the basic concept, we will have to look beyond the modern conceptual boundaries of Space-Time, and Materialism. And that may sound closer to Religion than Science. But, it's intended to be merely an update of Science and Philosophy, with Religion as an optional consideration. It's not a simple explanation, because it requires a shift in worldview.

The percepts of Pleasure and Pain, are conceived in religious terms as Good and Evil, or in scientific terms as Negentropy or Entropy. But in my thesis all of these percepts and concepts are defined in terms of the 21st century notion of ubiquitous Information, which bridges the old gap between Body & Mind, Science & Religion, Sensation & Feelings, and between Quanta & Qualia. But that's probably not the kind of answer you were hoping for.

why is damage to the body or satiation accompanied by a qualitative feeling rather than simply being perception — Enrique

I have been entertaining a hypothesis on that for many years, and I still hold it possible, if not plausible, if not actual. That is, in my model of consciousness as quasi-stable, dynamic standing wave resonance w/in our brains, anything that disrupts the stability of the resonant condition may be experienced as a qualia pain. One evidence for this hypothesis includes the fact that pain forces (consumes) ones conscious to focus on and experience nothing but the (discord) pain. Another evidence I have for this hypothesis is the actual pain people suffering from Epilepsy experience during an Epileptic seizure (discord in brain waves), which pain can be removed by electric shock to the brain like a defibrillator restoring the resonant heart beat condition. Also, the mental pain of a 'broken heart' causes a discord in consciousness thought.

hope this elevates the discussion here...

That is, in my model of consciousness as quasi-stable, dynamic standing wave resonance w/in our brains, anything that disrupts the stability of the resonant condition may be experienced as a qualia pain — Sir Philo Sophia

My eventual conclusion was very similar, that qualia of all types - feelings, sensations, perceptions and so on - are the additive properties of superpositioned and entangled particle and EMF wavelengths further integrated and synchronized by neuromatter tissues such as neurons and glia. Standing brain waves as registered by an EEG are those additive properties at the macroscopic, currently observable level.

so, then, if consciousness as quasi-stable, dynamic standing wave resonance (quantum, entangled, or whatever) w/in our brains, why would inducing altered states of mind (alcohol, drugs, pot, hypnosis, meditation, etc.) reduce or lessen or remove the qualia sense of pain. e.g., how could hypnosis program your brain/consciousness to not let pain sensors disrupt it? That is, if the qualia of pain is relatively easily mentally programmable then it would seem not be be a resonant state disruption mechanism, but more of a connectionist upregulation/downregulation circuit model The standard connectionist model pretty much has no qualia requirements or capacity. so, there is something more...

Qualia as quantum is simply a different mechanistic framework to perhaps more widely and inclusively model the same and maybe further substances. Altered states of consciousness could be induced by changes to wavicle/EMF patterns in addition to the traditional, only fractional explanation provided by analysis of neurotransmitter concentrations and neuron synapsing in general. If possible, researching the impact of hallucinogens on cells might identify molecular loci of entanglement and superposition effects in the body, qualia's deep structure. If this line of examination proves fruitful, more perceptive real time scanning will ideally be developed to make qualitative phenomena scientifically observable in a non-invasive way.

why is damage to the body or satiation accompanied by a qualitative feeling rather than simply being perception — Enrique

It seems obvious enough: We experience sensations with emotions (and 'qualitative' assessment) because our brains have evolved to do precisely that.

The many physical sensations we can experience (pleasure, cold, heat, pain, pressure, hunger, tickling, satiation, etc.) are interpreted in the light of meanings which are assigned. Various perceptions will be interpreted with more or less emotion and qualitative evaluation, depending on the meaning that can be assigned to a perception. A sense of alarm might be registered as you watch the tally on your groceries greatly exceed what you expected. The sensations of desired sexual contact are likely to be received positively. The usually unpleasant sensations associated with a dental drill may be welcome, in the light o the severe toothache which brought you to the dentist.

Fortunately, we do not experience everything with rich emotional or qualitative interpretation. A large share of our perceptions are received quite mechanically. A great deal of perception is utilitarian,. the numbers on gauges in a factory or lab are likely to be perceived in a utilitarian fashion, without feeling.

Presumably some animals with very simple brains do perceive in a very functional S/R manner. A simple worm, for instance, doesn't have enough neurons to do more than a simple SR. I'm not sure what insect brains are like; does a grasshopper feel anything? Could be, don't know. But once we get into larger more complex brains, perceptions become more complex