CONCEPT
What It Is Like
Thomas Nagel's four-word formulation—an organism has conscious mental states if and only if there is something it is like to be that organism—which serves as the philosophical marker for subjective experience and the measuring instrument for what no external investigation can detect.
In 1974, Thomas Nagel needed a phrase that would mark, with the precision of a technical term and the naturalness of ordinary language, the feature of
consciousness that every reductive theory had failed to capture. He found it in an ordinary English construction:
what it is like. An organism has conscious mental states, Nagel proposed, if and only if there is something it is like to be that organism—something it is like for the organism, not merely for an outside observer. Read quickly, the phrase seems tautological. Of course there is something it is like to taste coffee. Of course there is something it is like to feel pain. But Nagel's achievement was to demonstrate that this obvious fact is precisely what every reductive account leaves out—and that the omission is not a gap to be filled later by more neuroscience but a structural absence produced by the choice of method.