The 
hard problem of consciousness is the problem of explaining how and why we have 
qualia or 
phenomenal experiences — how sensations acquire characteristics, such as colours and tastes.
[1] David Chalmers, who introduced the term "hard problem" of consciousness,
[2]
 contrasts this with the "easy problems" of explaining the ability to 
discriminate, integrate information, report mental states, focus 
attention, etc. Easy problems are easy because all that is required for 
their solution is to specify a mechanism that can perform the function. 
That is, their proposed solutions, regardless of how complex or poorly 
understood they may be, can be entirely consistent with the modern 
materialistic conception of natural phenomena. Chalmers claims that the 
problem of experience is distinct from this set, and he argues that the 
problem of experience will "persist even when the performance of all the
 relevant 
functions is explained".
[3]
The existence of a "hard problem" is controversial and has been disputed by some philosophers.
[4][5]
 Providing an answer to this question could lie in understanding the 
roles that physical processes play in creating consciousness and the 
extent to which these processes create our subjective qualities of 
experience.
[3]
Several questions about consciousness must be resolved in order to 
acquire a full understanding of it. These questions include, but are not
 limited to, whether being conscious could be wholly described in 
physical terms, such as the aggregation of neural processes in the 
brain. If consciousness 
cannot be explained exclusively by 
physical events, it must transcend the capabilities of physical systems 
and require an explanation of nonphysical means. For philosophers who 
assert that consciousness is nonphysical in nature, there remains a 
question about what outside of physical theory is required to explain 
consciousness.
Formulation of the problem
Chalmers' formulation
In 
Facing Up to the Problem of Consciousness, Chalmers wrote:
[3]
| “ | It is 
undeniable that some organisms are subjects of experience. But the 
question of how it is that these systems are subjects of experience is 
perplexing. Why is it that when our cognitive systems engage in visual 
and auditory information-processing, we have visual or auditory 
experience: the quality of deep blue, the sensation of middle C? How can
 we explain why there is something it is like to entertain a mental 
image, or to experience an emotion? It is widely agreed that experience 
arises from a physical basis, but we have no good explanation of why and
 how it so arises. Why should physical processing give rise to a rich 
inner life at all? It seems objectively unreasonable that it should, and
 yet it does. | ” | 
Easy problems
Chalmers contrasts the Hard Problem with a number of (relatively) 
Easy Problems that consciousness presents. (He emphasizes that what the 
easy problems have in common is that they all represent some ability, or
 the performance of some function or behavior).
- the ability to discriminate, categorize, and react to environmental stimuli;
- the integration of information by a cognitive system;
- the reportability of mental states;
- the ability of a system to access its own internal states;
- the focus of attention;
- the deliberate control of behavior;
- the difference between wakefulness and sleep.
Other formulations
Various formulations of the "hard problem":
- "How is it that some organisms are subjects of experience?"
- "Why does awareness of sensory information exist at all?"
- "Why do qualia exist?"
- "Why is there a subjective component to experience?"
- "Why aren't we philosophical zombies?"
James Trefil notes that "it is the only major question in the sciences that we don't even know how to ask."
[6]
Historical predecessors
The hard problem has scholarly antecedents considerably earlier than Chalmers.
Gottfried Leibniz wrote, as an example also known as 
Leibniz's gap:
Moreover, it must be confessed that perception and that which depends
 upon it are inexplicable on mechanical grounds, that is to say, by 
means of figures and motions. And supposing there were a machine, so 
constructed as to think, feel, and have perception, it might be 
conceived as increased in size, while keeping the same proportions, so 
that one might go into it as into a mill. That being so, we should, on 
examining its interior, find only parts which work one upon another, and
 never anything by which to explain a perception.[7]
Isaac Newton wrote in a letter to 
Henry Oldenburg:
to determine by what modes or actions light produceth in our minds the phantasm of colour is not so easie.[8]
T.H. Huxley remarked:
how it is that any thing so remarkable as a state of consciousness 
comes about as the result of irritating nervous tissue, is just as 
unaccountable as the appearance of the Djin when Aladdin rubbed his 
lamp.[9]
Responses
Scientific attempts
There have been scientific attempts to explain subjective aspects of consciousness, which is related to the 
binding problem in neuroscience. Many eminent theorists, including 
Francis Crick and 
Roger Penrose,
 have worked in this field. Nevertheless, even as sophisticated accounts
 are given, it is unclear if such theories address the hard problem. 
Eliminative materialist philosopher 
Patricia Smith Churchland has famously remarked about Penrose's theories that "Pixie dust in the synapses is about as explanatorily powerful as 
quantum coherence in the 
microtubules."
[10]
Consciousness is fundamental or elusive
Some philosophers, including 
David Chalmers and 
Alfred North Whitehead, argue that conscious experience is a fundamental constituent of the universe, a form of 
panpsychism sometimes referred to as 
panexperientialism.
 Chalmers argues that a "rich inner life" is not logically reducible to 
the functional properties of physical processes. He states that 
consciousness must be described using nonphysical means. This 
description involves a fundamental ingredient capable of clarifying 
phenomena that has not been explained using physical means. Use of this 
fundamental property, Chalmers argues, is necessary to explain certain 
functions of the world, much like other fundamental features, such as 
mass and time, and to explain significant principles in nature.
Thomas Nagel
 has posited that experiences are essentially subjective (accessible 
only to the individual undergoing them), while physical states are 
essentially objective (accessible to multiple individuals). So at this 
stage, we have no idea what it could even mean to claim that an 
essentially subjective state just 
is an essentially non-subjective state. In other words, we have no idea of what reductivism really amounts to.
[11]
New mysterianism, such as that of 
Colin McGinn, proposes that the human mind, in its current form, will not be able to explain consciousness.
[12]
Deflationary accounts
Some philosophers, such as 
Daniel Dennett,
[4] Stanislas Dehaene,
[5] and 
Peter Hacker,
[13]
 oppose the idea that there is a hard problem. These theorists argue 
that once we really come to understand what consciousness is, we will 
realize that the hard problem is unreal. For instance, Dennett asserts 
that the so-called hard problem will be solved in the process of 
answering the easy ones.
[4]
 In contrast with Chalmers, he argues that consciousness is not a 
fundamental feature of the universe and instead will eventually be fully
 explained by natural phenomena. Instead of involving the nonphysical, 
he says, consciousness merely plays tricks on people so that it appears 
nonphysical—in other words, it simply seems like it requires nonphysical
 features to account for its powers. In this way, Dennett compares 
consciousness to stage magic and its capability to create extraordinary 
illusions out of ordinary things.
[14]
To show how people might be commonly fooled into overstating the 
powers of consciousness, Dennett describes a normal phenomenon called 
change blindness, a visual process that involves failure to detect scenery changes in a series of alternating images.
[15]
 He uses this concept to argue that the overestimation of the brain's 
visual processing implies that the conception of our consciousness is 
likely not as pervasive as we make it out to be. He claims that this 
error of making consciousness more mysterious than it is could be a 
misstep in any developments toward an effective explanatory theory. 
Critics such as Galen Strawson reply that, in the case of consciousness,
 even a mistaken experience retains the essential face of experience 
that needs to be explained, contra Dennett.
To address the question of the hard problem, or how and why physical 
processes give rise to experience, Dennett states that the phenomenon of
 having experience is nothing more than the performance of functions or 
the production of behavior, which can also be referred to as the easy 
problems of consciousness.
[4]
 He states that consciousness itself is driven simply by these 
functions, and to strip them away would wipe out any ability to identify
 thoughts, feelings, and consciousness altogether. So, unlike Chalmers 
and other dualists, Dennett says that the easy problems and the hard 
problem cannot be separated from each other. To him, the hard problem of
 experience is included among—not separate from—the easy problems, and 
therefore they can only be explained together as a cohesive unit.
[14]
Dehaene's argument has similarities with those of Dennett. He says 
Chalmers' 'easy problems of consciousness' are actually the hard 
problems and the 'hard problems' are based only upon intuitions that, 
according to Dehaene, are continually shifting as understanding evolves.
 "Once our intuitions are educated ...Chalmers' hard problem will 
evaporate" and "
qualia...will be viewed as a peculiar idea of the prescientific era, much like 
vitalism...[Just
 as science dispatched vitalism] the science of consciousness will eat 
away at the hard problem of consciousness until it vanishes."
[5]
Like Dennett, 
Peter Hacker
 argues that the hard problem is fundamentally incoherent and that 
"consciousness studies," as it exists today, is "literally a total waste
 of time:"
[13]
- “The whole endeavour of the consciousness studies community is 
absurd – they are in pursuit of a chimera. They misunderstand the nature
 of consciousness. The conception of consciousness which they have is 
incoherent. The questions they are asking don’t make sense. They have to
 go back to the drawing board and start all over again.”
Critics of Dennett's approach, such as 
David Chalmers and 
Thomas Nagel,
 argue that Dennett's argument misses the point of the inquiry by merely
 re-defining consciousness as an external property and ignoring the 
subjective aspect completely. This has led detractors to refer to 
Dennett's book 
Consciousness Explained as 
Consciousness Ignored or 
Consciousness Explained Away.
[4] Dennett discussed this at the end of his book with a section entitled 
Consciousness Explained or Explained Away?[15]
Glenn Carruthers and Elizabeth Schier argue that the main arguments for the existence of a hard problem -- 
philosophical zombies, 
Mary's room, and 
Nagel's bats
 -- are only persuasive if one already assumes that "consciousness must 
be independent of the structure and function of mental states, i.e. that
 there is a hard problem." Hence, the arguments 
beg the question.
 The authors suggest that "instead of letting our conclusions on the 
thought experiments guide our theories of consciousness, we should let 
our theories of consciousness guide our conclusions from the thought 
experiments."
 Contrary to this line of argument, Chalmers says: "Some may be led to 
deny the possibility [of zombies] in order to make some theory come out 
right, but the justification of such theories should ride on the 
question of possibility, rather than the other way round".
[17]:96
A notable deflationary account is the Higher-Order Thought theories of consciousness.
[18][19] Peter Carruthers
 discusses "recognitional concepts of experience", that is, "a capacity 
to recognize [a] type of experience when it occurs in one's own mental 
life", and suggests such a capacity does not depend upon qualia.
[20] Though the most common arguments against deflationary accounts and 
eliminative materialism is the argument from 
qualia,
 and that conscious experiences are irreducible to physical states - or 
that current popular definitions of "physical" are incomplete - the 
objection follows that the one and same reality can appear in different 
ways, and that the numerical difference of these ways is consistent with
 a unitary mode of existence of the reality. Critics of the deflationary
 approach object that qualia are a case where a single reality cannot 
have multiple appearances. As 
John Searle points out: "where consciousness is concerned, the existence of the appearance is the reality."
[21]
Massimo Pigliucci
 distances himself from eliminativism, but he insists that the hard 
problem is still misguided, resulting from a "category mistake":
[22]
- Of course an explanation isn't the same as an experience, but that’s
 because the two are completely independent categories, like colors and 
triangles. It is obvious that I cannot experience what it is like to be 
you, but I can potentially have a complete explanation of how and why it
 is possible to be you.
References
-  Stevan Harnad (1995). "Why and How We Are Not Zombies". Journal of Consciousness Studies 1: 164–167.
-  See Cooney's foreword to the reprint of Chalmers' paper: Brian Cooney, ed, ed. (1999). "Chapter=27: Facing up to the problem of consciousness". The Place of Mind. Cengage Learning. pp. 382 ff. ISBN 0534528252.
-  David Chalmers (1995). "Facing Up to the Problem of Consciousness"". Journal of Consciousness Studies 2 (3): 200–219. See also this link
-  Daniel C. Dennett (2013). "The tuned deck". Intuition Pumps And Other Tools for Thinking. W. W. Norton & Company. pp. 310 ff. ISBN 0393240681. and also "Commentary on Chalmers": Dennett, Daniel C. (1996). "Facing backwards on the problem of consciousness". Journal of Consciousness Studies 3 (1): 4–6.
-  Stanislas Dehaene (2014). Consciousness and the Brain: Deciphering How the Brain Codes Our Thoughts. Viking Adult. p. 197. ISBN 0670025437.
-  James S Trefil (1997). "Chapter 3: Will we ever understand consciousness?". One hundred and one things you don't know about science and no one else does either. Mariner Books. p. 15. ISBN 0-395-87740-7.
-  Leibniz, Monadology, 17, as quoted by Istvan Aranyosi (2004). "Chalmers's zombie arguments" (draft ed.). Central European University Personal Pages.
-  Stanford Encyclopedia of Philosophy on Panpsychism
-  The Elements of Physiology and Hygiene: A Text-book for Educational Institutions, by T.H. Huxley & W.J. Youmans. Appleton & Co., 1868 p. 178
-  Churchland, Patricia Smith (2002). Brain-wise: studies in neurophilosophy. MIT Press. p. 197. ISBN 0-262-53200-X.
-  Nagel, Thomas. "What is it like to be a bat?". Retrieved 9 December 2013.
-  Colin McGinn (20 February 2012). "All machine and no ghost?". New Statesman. Retrieved 27 March 2012.
-  Peter Hacker (2010). "Hacker's challenge". The Philosopher's Magazine 51 (51): 23–32.
-  Daniel Dennett (2003). "Explaining the "Magic" of Consciousness". Journal of Cultural and Evolutionary Psychology 1 (1): 7–19. doi:10.1556/jcep.1.2003.1.2. See also this link.
-  Daniel Dennett (1993). Consciousness Explained (Paperback ed.). Penguin Group. ISBN 0140128670.
-  David J. Chalmers (1996). The Conscious Mind: In Search of a Fundamental Theory. New York and Oxford: Oxford University Press.
-  The HOT theory and Antitheories
-  Carruthers, Peter. "Higher-Order Theories of Consciousness". Stanford Encyclopedia of Philosophy.
-  Peter Carruthers (2005). "Phenomenal concepts and higher-order experiments". Consciousness: Essays from a Higher-Order Perspective. Oxford University Press. pp. 79 ff. ISBN 0191535044.
-  Searle, J.The Mystery of Consciousness, p111
-  Massimo Pigliucci (2013). "What Hard Problem?". Philosophy Now (99).
 
Further reading
External links