In philosophy of mind, the hard problem of consciousness is to explain how and why organisms have qualia, phenomenal consciousness, or subjective experience. It is contrasted with the "easy problems"
David Chalmers on stage for an Alan Turing Year event at De La Salle University, Manila, 27 March 2012
The hard problem is often illustrated by appealing to the logical possibility of inverted visible spectra. If there is no logical contradiction in supposing that one's colour vision could be inverted, it follows that mechanistic explanations of visual processing do not determine facts about what it is like to see colours.
David Chalmers
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David John Chalmers is an Australian philosopher and cognitive scientist, specializing in philosophy of mind and philosophy of language. He is a professor of philosophy and neural science at New York
Hard problem of consciousness
…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. The following year, the main talking points of Chalmers' talk…
Chalmers in 2021
David Chalmers with Toby Walsh at AAAI Conference 2025, Philadelphia