In philosophy, being means the material or immaterial existence of a thing. Anything that exists is being. Ontology is the branch of philosophy that studies being. Being is a concept encompassing objective and subjective features of reality and existence. Anything that partakes in being is also called a "being", though often this usage is limited to entities that have subjectivity (as in the expression "human being"). The notion of "being" has, inevitably, been elusive and controversial in the history of philosophy, beginning in Western philosophy with attempts among the pre-Socratics to deploy it intelligibly. The first effort to recognize and define the concept came from Parmenides, who famously said of it that "what is-is". Common words such as "is", "are", and "am" refer directly or indirectly to being.
As an example of efforts in recent times, the German philosopher Martin Heidegger (1889-1976) (who himself drew on ancient Greek sources) adopted German terms like Dasein to articulate the topic. Several modern approaches build on such continental European exemplars as Heidegger, and apply metaphysical results to the understanding of human psychology and the human condition generally (notably in the existentialist tradition). By contrast, in mainstream analytical philosophy the topic is more confined to abstract investigation, in the work of such influential theorists as W. V. O. Quine (1908-2000), to name one of many. One of the most fundamental questions that has been contemplated in various cultures and traditions (e.g., Native American) and continues to exercise philosophers was articulated thus by William James (1842-1910) in 1909: "How comes the world to be here at all instead of the nonentity which might be imagined in its place? ... from nothing to being there is no logical bridge."