This volume presents a series of essays published by Charles Kahn over a period of forty years, in which he seeks to explicate the ancient Greek concept of Being. He addresses two distinct but intimately related problems, one linguistic and one historical and philosophical. The linguistic problem concerns the theory of the Greek verb einai, `to be`: how to replace the conventional but misleading distinction between copula and existential verb with a more adequate theoretical account. The philosophical problem is in principle quite distinct: to understand how the concept of Being became the central topic in Greek philosophy from Parmenides to Aristotle. But these two problems converge on what Kahn calls the veridical use of einai. In the earlier papers he takes that connection between the verb and the concept of truth to be the key to the central role of Being in Greek philosophy. In the later papers he interprets the veridical in terms of a more general semantic function of the verb, which comprises the notions of existence and instantiation as well as truth.