We rely on the strength of linguistic and philosophical perspectives in constructing a framework that offers a unified explanation for presuppositions and existential commitment. We use a rich ontology and a set of methodological principles that embed the essence of Meinong's philosophy and Grice's conversational principles into a stratified logic, under an unrestricted interpretation of the quantifiers. The result is a logical formalism that yields a tractable computational method that uniformly calculates all the presuppositions of a given utterance, including the existential ones.