Hard problem of consciousness

In the philosophy of mind, the hard problem of consciousness is to explain why and how humans and other organisms have qualia, phenomenal consciousness, or subjective experience.^[1][2] It is contrasted with the "easy problems" of explaining why and how physical systems give a (healthy) human being the ability to discriminate, to integrate information, and to perform behavioral functions such as watching, listening, speaking (including generating an utterance that appears to refer to personal behaviour or belief), and so forth.^[1] The easy problems are amenable to functional explanation—that is, explanations that are mechanistic or behavioral—since each physical system can be explained (at least in principle) purely by reference to the "structure and dynamics" that underpin the phenomenon.^[1][3]

Proponents of the hard problem argue that it is categorically different from the easy problems since no mechanistic or behavioral explanation could explain the character of an experience, not even in principle. Even after all the relevant functional facts are explicated, they argue, there will still remain a further question: "why is the performance of these functions accompanied by experience?"^[1] To bolster their case, proponents of the hard problem frequently turn to various philosophical thought experiments, involving philosophical zombies (which, they claim, are conceivable) or inverted qualia, or the claimed ineffability of colour experiences, or the claimed unknowability of foreign states of consciousness, such as the experience of being a bat.

The terms "hard problem" and "easy problems" were coined by the philosopher David Chalmers in a 1994 talk given at The Science of Consciousness conference held in Tucson, Arizona.^[4] The following year, the main talking points of Chalmers' talk were published in The Journal of Consciousness Studies.^[1] The publication gained significant attention from consciousness researchers and became the subject of a special volume of the journal,^[5][6] which was later published into a book.^[7] In 1996, Chalmers published The Conscious Mind, a book-length treatment of the hard problem, in which he elaborated on his core arguments and responded to counterarguments. His use of the word easy is "tongue-in-cheek".^[8] As the cognitive psychologist Steven Pinker puts it, they are about as easy as going to Mars or curing cancer. "That is, scientists more or less know what to look for, and with enough brainpower and funding, they would probably crack it in this century."^[9]

The existence of the hard problem is disputed. It has been accepted by some philosophers of mind such as Joseph Levine,^[10] Colin McGinn,^[11] and Ned Block^[12] and cognitive neuroscientists such as Francisco Varela,^[13] Giulio Tononi,^[14][15] and Christof Koch.^[14][15] On the other hand, its existence is denied by other philosophers of mind, such as Daniel Dennett,^[16] Massimo Pigliucci,^[17] Thomas Metzinger, Patricia Churchland,^[18] and Keith Frankish,^[19] and by cognitive neuroscientists such as Stanislas Dehaene,^[20] Bernard Baars,^[21] Anil Seth,^[22] and Antonio Damasio.^[23] Clinical neurologist and skeptic Steven Novella has dismissed it as "the hard non-problem".^[24] According to a 2020 PhilPapers survey, a majority (62.42%) of the philosophers surveyed said they believed that the hard problem is a genuine problem, while 29.72% said that it does not exist.^[25]

There are a number of other potential philosophical problems that are related to the Hard Problem. Ned Block believes that there exists a "Harder Problem of Consciousness", due to the possibility of different physical and functional neurological systems potentially having phenomenal overlap.^[12] Another potential philosophical problem which is closely related to Benj Hellie's vertiginous question, dubbed "The Even Harder Problem of Consciousness", refers to why a given individual has their own particular personal identity, as opposed to existing as someone else.^[26]