Reductionism is any of several related philosophical ideas regarding the associations between phenomena which can be described in terms of other simpler or more fundamental phenomena. It is also described as an intellectual and philosophical position that interprets a complex system as the sum of its parts.

Thomas Nagel is an American philosopher. He is the University Professor of Philosophy and Law Emeritus at New York University, where he has taught since 1980, retiring in 2016. His main areas of philosophical interest are legal philosophy, political philosophy, and ethics.