Edmund Husserl, the founder of phenomenology, sought to establish philosophy as a rigorous science by returning "to the things themselves." He argued that philosophy should not begin with speculative metaphysical assumptions or empirical generalizations but with the careful description of conscious experience as it is directly lived. Phenomenology is, therefore, the systematic study of phenomena as they appear to consciousness. Husserl believed that by examining the structures of experience, philosophy could discover universal truths about consciousness and knowledge. According to Husserl, consciousness is not an isolated entity containing ideas or representations. Instead, consciousness is always conscious of something. This fundamental characteristic of consciousness is known as intentionality. Borrowing and refining a concept from Franz Brentano, Husserl argued that every act of consciousness is directed toward an object, whether the object exists in reality or is merely imagined. Perceiving a tree, remembering a childhood event, desiring success, fearing failure, or imagining a mythical creature are all intentional acts because they involve consciousness relating to an object. Intentionality implies that consciousness and its object are inseparable in experience. Consciousness cannot exist as empty awareness without an object, nor can objects become meaningful apart from their appearance to consciousness.