Qualia
The individual instances of subjective, conscious experience, such as how one perceives of taste, or of color.
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Origin
Charles Sanders Peirce introduced the singular quale in philosophy in his 1866 Lowell Lectures, but the plural "qualia" entered its modern sense through C. I. Lewis's Mind and the World-Order (1929), which described purely subjective, recognisable characters of sensory experience. The concept gained mainstream currency when Thomas Nagel's 1974 essay "What Is It Like to Be a Bat?" posed whether subjective experience could ever be explained in physical terms, making qualia the centrepiece of philosophy of mind.
Updated February 22, 2026