linguistic:voice_change, stylistic:tone
Formal and regional ontology

Husserl sees ontology as a science of essences. Sciences of essences are contrasted with factual sciences: the former are knowable a priori and provide the foundation for the later, which are knowable a posteriori. Ontology as a science of essences is not interested in actual facts, but in the essences themselves, whether they have instances or not. Husserl distinguishes between formal ontology, which investigates the essence of objectivity in general, and regional ontologies, which study regional essences that are shared by all entities belonging to the region. Regions correspond to the highest genera of concrete entities: material nature, personal consciousness and interpersonal spirit. Husserl's method for studying ontology and sciences of essence in general is called eidetic variation. It involves imagining an object of the kind under investigation and varying its features. The changed feature is inessential to this kind if the object can survive its change, otherwise it belongs to the kind's essence. For example, a triangle remains a triangle if one of its sides is extended but it ceases to be a triangle if a fourth side is added. Regional ontology involves applying this method to the essences corresponding to the highest genera.