Since at least Verkuyl (1972), aktionsart has been considered a property of phrasal configurations minimally resulting from a combination of a predicate and its internal argument. This has been demonstrated most clearly in the literature on telicity where certain predicate-argument configurations allow for a telic interpretation while others permit only an atelic interpretation. The properties shared by nominals and events and the manner of their composition has been the source of much debate, leading to a rich literature on the composition of events. Largely left out of this debate, however, has been the role that arguments might play, if any at all, in the composition of states. This dissertation explores the role arguments and predicates play in determining the availability of an existential interpretation of a stative subject, one property distinguishing between the stage-level and individual-level behavior of predicates. It develops a theory of aktionsart in which quantization, the opposition of quantized and homogeneous structures, plays a central role in determining the aspectual behavior of stative predicates. It argues that the distinction between stage-level and individual-level states is determined compositionally, taking into account properties of the predicate, both verbal and adjectival, and its arguments. I begin by observing two empirical puzzles which affect the availability of existential interpretation: the effects of internal arguments in verbal statives first observed in Fernald (1994) and the scale structure effects of adjectival predicates. Pursuing an analogy between the availability of existential interpretation in states and telicity in events, I explore the possible role verbs in stative predicates play in determining the existential interpretation of their subject, ultimately arguing that there are no individual-level or stage-level verbs. I then turn to the role played by verbal arguments in stative predicates. I propose, in opposition to topic-comment theories of the internal argument effects, that the quantization of the object of transitive stative verbs determines whether they license an existential interpretation of their subject. Predicates with quantized objects license an existential interpretation, while those with homogeneous objects do not. Given the structural analogy between the availability of existential interpretation and telicity, I propose that stative and eventive predicates are composed by the same mechanisms, with the distinction between states and events arising from the selectional restrictions on Voice, following Kratzer (1996, 2004). I then turn to adjectival predicates and the observation that their scale structure influences the availability of existential interpretation. I demonstrate that scale structure is a type of quantization (closed scales are quantized; open scales are homogeneous) and argue that this compositionally determines their stage-level/individual-level behavior. I further consider the role arguments play in determining the availability of existential interpretation, observing that, as with telicity, the quantization of arguments affects a predicate's stage-level/individual-level behavior. The dissertation closes with an overview of its content and presents a highly speculative discussion on the role played by quantization in language and the possible role it may play in vision, suggesting that quantization may be a core component of cognition more generally. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]