This book is a monograph study of Ingarden’s investigations into existence. Its aim is to give a clear and formally precise account, as well as a critical evaluation, of his contributions. In the first chapter the basic principles of Ingarden’s ontology are reformulated and, contrary to Ingarden, a nominalistic point of view is adopted. Chapters 2 to 4 give a reconstruction of the arguments for the following Ingardenian theses: (1) Existence is not a property; (2) The concept of existence is a principle sui generis of classification; (3) exist(s) is an equivocal word. On the basis of this critical doxography Chapters 5 and 6 provide a systematic examination of the Ingardenian position, by confronting it with the results of analytic philosophy (such as early Husserl, Frege, Russell, Moore, Meinong, Bergmann, Hochberg, Castaneda).