If I look at the color of a pair of socks inside a gloomy shop, it may appear differently to me compared with how it appears outside in bright daylight; if I am pricked by a needle on different occasions, my experience feels a certain way to me, and it might also well vary with my mood or attention. To use a more important example, one might also think of the distinctive kind of anxiety or depressive feeling a psychiatric patient

suffers from when faced with Inhibitors,research,lifescience,medical a situation that healthy people perhaps find merely a bit worrying. However, regardless of such variations, what is most important about the qualia of feelings and perceptions is that they are distinctive to these mental states: they would not be what they are if they did not possess certain qualitative features. Are qualia reducible to material Inhibitors,research,lifescience,medical states of the brain? This is sometimes said to be “the”—the only, or the most difficult, or the “hard”—problem of consciousness.4

Skepticism has often been the default position, not only among philosophers but among cognitive scientists as well: “EPZ5676 Consciousness is a fascinating but elusive phenomenon; it is impossible to specify what it is, what it does, or why it evolved. Nothing worth reading has been written about it.5 ” John Searle makes a different but Inhibitors,research,lifescience,medical related point: “Until recently, most neuroscientists did not regard consciousness as a suitable topic for scientific investigation. This reluctance was based on certain philosophical mistakes, primarily Inhibitors,research,lifescience,medical the mistake of supposing that the subjectivity of consciousness made it beyond the reach of an objective science.6 ” Nowadays, in influential encyclopedia entries, one also reads such musings as: “Questions about the nature of conscious awareness have likely been asked for as long as there have been humans.”7 This is probably not so;

and even if one “merely” claims that the topic of consciousness Inhibitors,research,lifescience,medical has been around since ancient times, that is misleading too. The problem of whether states of phenomenal consciousness can be identified with appropriate brain states cannot be found in Descartes or Kant. Attempts to read it into those and other authors distort their assumptions, arguments, and indeed their whole agendas.8,9 For much of the 20th century, discussions about qualia often arose from epistemological questions—How do we know that a certain system has states of phenomenal qualia?—or Cell press from semantic problems—What is the precise meaning of the relevant terms?10-12 U. T. Place,13 J. J. C. Smart,14 and others defended the idea that the mind is simply the brain, with new arguments. Their “reductive physicalism” was in turn attacked, especially in influential papers by Thomas Nagel,15 Frank Jackson,16,17 and Joseph Levine.18 Du Bois-Reymond’s skepticism was revived in various ways, provoking a flood of consciousness studies over recent years.