Qualia


In philosophy of mind, qualia are defined as instances of subjective, conscious experience. The term qualia derives from the Latin neuter plural form of the Latin adjective quālis meaning "of what sort" or "of what kind" in relation to a specific instance, such as "what it is like to taste a specific this particular apple now".
Examples of qualia include the perceived sensation of pain of a headache, the taste of wine, and the redness of an evening sky. As qualitative characteristics of sensations, qualia stand in contrast to propositional attitudes, where the focus is on beliefs about experience rather than what it is directly like to be experiencing.
C.S. Peirce introduced the term quale in philosophy in 1866, and in 1929 C. I. Lewis was the first to use the term "qualia" in its generally agreed-upon modern sense. Frank Jackson later defined qualia as "...certain features of the bodily sensations especially, but also of certain perceptual experiences, which no amount of purely physical information includes". Philosopher and cognitive scientist Daniel Dennett suggested that qualia was "an unfamiliar term for something that could not be more familiar to each of us: the ways things seem to us".
The nature and existence of qualia under various definitions remain controversial. Much of the debate over the importance of qualia hinges on the definition of the term, and various philosophers emphasize or deny the existence of certain features of qualia.

Definitions

Many definitions of qualia have been proposed. One of the simpler, broader definitions is: "The 'what it is like' character of mental states. The way it feels to have mental states such as pain, seeing red, smelling a rose, etc."
Leibniz's passage in his Monadology in 1714 described the explanatory gap as follows:
It must be confessed, moreover, that perception, and that which depends on it, are inexplicable by mechanical causes, that is, by figures and motions. And, supposing that there were a mechanism so constructed as to think, feel and have perception, we might enter it as into a mill. And this granted, we should only find on visiting it, pieces which push one against another, but never anything by which to explain a perception. This must be sought, therefore, in the simple substance, and not in the composite or in the machine.

Charles Sanders Peirce introduced the term quale in philosophy in 1866, and in 1929 C.I. Lewis was the first to use the term "qualia" in its generally agreed upon modern sense.
Frank Jackson later defined qualia as "...certain features of the bodily sensations especially, but also of certain perceptual experiences, which no amount of purely physical information includes".
Daniel Dennett suggested that qualia was "an unfamiliar term for something that could not be more familiar to each of us: the ways things seem to us". He identifies four properties that are commonly ascribed to qualia. According to these, qualia are:
  1. ineffable – they cannot be communicated, or apprehended by any means other than direct experience.
  2. intrinsic – they are non-relational properties, which do not change depending on the experience's relation to other things.
  3. private – all interpersonal comparisons of qualia are systematically impossible.
  4. directly or immediately apprehensible by consciousness – to experience a quale is to know one experiences a quale, and to know all there is to know about that quale.
If qualia of this sort exist, then a normally sighted person who sees red would be unable to describe the experience of this perception in such a way that a listener who has never experienced color will be able to know everything there is to know about that experience. Though it is possible to make an analogy, such as "red looks hot", or to provide a description of the conditions under which the experience occurs, such as "it's the color you see when light of 700-nm wavelength is directed at you", supporters of this definition of qualia contend that such descriptions cannot provide a complete description of the experience.
Another way of defining qualia is as "raw feels". A raw feel is a perception in and of itself, considered entirely in isolation from any effect it might have on behavior and behavioral disposition. In contrast, a cooked feel is that perception seen in terms of its effects. For example, the perception of the taste of wine is an ineffable, raw feel, while the behavioral reaction one has to the warmth or bitterness caused by that taste of wine would be a cooked feel. Cooked feels are not qualia.
Arguably, the idea of hedonistic utilitarianism, where the ethical value of things is determined from the amount of subjective pleasure or pain they cause, is dependent on the existence of qualia.

Arguments regarding the existence of qualia

Since, by definition, qualia cannot be fully conveyed verbally, they also cannot be demonstrated directly in an argument – a more nuanced approach is needed. Arguments for qualia generally come in the form of thought experiments designed to lead one to the conclusion that qualia exist.

Modern philosophy

Inverted spectrum argument

The inverted spectrum thought experiment, originally developed by John Locke, invites us to imagine two individuals who perceive colors differently: where one person sees red, the other sees green, and vice versa. Despite this difference in their subjective experiences, they behave and communicate as if their perceptions are the same, and no physical or behavioral test can reveal the inversion. Critics of functionalism, and of physicalism more broadly, argue that if we can imagine this happening without contradiction, it follows that we are imagining a change in a property that determines the way things look to us, but that has no physical basis.
The idea that an inverted spectrum would be undetectable in practice is also open to criticism on more scientific grounds, by C. L. Hardin, among others. As Alex Byrne puts it:
According to David Chalmers, all "functionally isomorphic" systems will have qualitatively identical conscious experiences. He calls this the principle of organizational invariance. For example, it implies that a silicon chip that is functionally isomorphic to a brain will have the same perception of the color red, given the same sensory inputs. He proposed the thought experiment of the "dancing qualia" to demonstrate this. It is a reductio ad absurdum argument that starts by supposing that two such systems can have different qualia in the same situation. It involves a switch that enables connecting the main part of the brain with either of these two subsystems. For example, one subsystem could be a chunk of brain that causes an object to appear red, and the other could be a silicon chip that causes the object to appear blue. Since both perform the same function within the brain, the subject would be unable to notice any change during the switch. Chalmers argues that this would be highly implausible if the qualia were truly switching between red and blue, hence the contradiction. Therefore, he concludes that the dancing qualia is impossible in practice, and the functionally isomorphic digital system would not only experience qualia, but it would have conscious experiences that are qualitatively identical to those of the biological system. He also proposed a similar thought experiment, named the fading qualia, that argues that it is not possible for the qualia to fade when each biological neuron is replaced by a functional equivalent.

Analytic philosophy

"What's it like to be?" argument

American philosopher Thomas Nagel's paper What Is it Like to Be a Bat? is often cited in debates about qualia, though it does not use the word "qualia". Nagel argues that consciousness has an essentially subjective character, a what-it-is-like aspect. He states that "an organism has conscious mental states if and only if there is something that it is like to be that organism – something it is like for the organism." Nagel suggests that this subjective aspect may never be sufficiently accounted for by the objective methods of reductionistic science. He claims that "if we acknowledge that a physical theory of mind must account for the subjective character of experience, we must admit that no presently available conception gives us a clue about how this could be done." Furthermore, "it seems unlikely that any physical theory of mind can be contemplated until more thought has been given to the general problem of subjective and objective."

Zombie argument

argues that one key consequence of the claim that such things as raw feels, or qualia, can be meaningfully discussed is that it leads to the logical possibility of two entities exhibiting identical behavior in all ways despite one of them entirely lacking qualia. While few claim that such an entity, called a philosophical zombie, actually exists, the possibility is raised as a refutation of physicalism, and in defense of the hard problem of consciousness.
The argument holds that it is conceivable for a person to have a duplicate, identical in every physical way, but lacking consciousness, called a "philosophical zombie." It would appear exactly the same as the original person, in both behavior and speech, just without subjective phenomenology. For these zombies to exist, qualia must not arise from any specific part or parts of the brain, for if it did there would be no difference between "normal humans" and philosophical zombies: The zombie/normal-human distinction can only be valid if subjective consciousness is separate from the physical brain.
According to Chalmers, the simplest form of the argument goes as follows:
  1. It is conceivable that there be zombies.
  2. If it is conceivable that there be zombies, it is metaphysically possible that there be zombies.
  3. If it is metaphysically possible that there be zombies, then consciousness is non-physical.
  4. Consciousness is nonphysical.
Former AI researcher Marvin Minsky sees the argument as circular. He says the proposition of something physically identical to a human but without subjective experience assumes that the physical characteristics of humans cannot produce consciousness, which is exactly what the argument claims to prove. In other words, it tries to prove consciousness is nonphysical by assuming consciousness is nonphysical.