Klinger recounts the history of how medieval Arabic philosophers in the Islamic East grappled with the logical role of the copula "to be," an ambiguity that has bedeviled Western philosophy from Parmenides to the analytic philosophers of today. Working from within a language that has no copula, a group of increasingly independent Arabic philosophers began to critically investigate the semantic role that Aristotle, for many centuries their philosophical authority, invested in the copula as the basis of his logic. Drawing on extensive manuscript research, Klinger breaks through the thicket of unstudied philosophical works to demonstrate the creativity of postclassical Islamic scholarship as it explored the consequences of its intellectual break with the past. Against the still widespread view that intellectual ferment all but disappeared during the period, he shows how these intellectuals over the centuries developed and refined a sophisticated philosophy of language that speaks to core concerns of contemporary linguistics and philosophy.