Plotinus was one of the most influential philosophers in antiquity after Plato and Aristotle. In his philosophy, there are three principles: the One, the Intellect, and the Soul. Historians of the 19th century invented the term Neoplatonism and applied it to Plotinus’ philosophy. His metaphysical writings have inspired centuries of Islamic, Jewish, Christian, and Gnostic metaphysicians. The issue of happiness is one of Plotinus’ greatest imprints on Western thought, as he was one of the first to introduce the idea that happiness is attainable only within consciousness.