Plotinus was a prominent philosopher in the 3rd century CE, known for founding the philosophical system called Neoplatonism. He emphasized the importance of the One, a transcendent source of all existence, from which everything emanates. His ideas sought to reconcile Plato's teachings with other philosophical and religious traditions of his time. His writings, compiled in the work known as the Enneads, explore concepts such as the nature of reality, the soul, and the process of returning to the One. Plotinus' influence extended to later thinkers, including Augustine and Renaissance philosophers, shaping the development of Western thought.