Plotinus was the last great philosopher of pagan antiquity, a systematizer of the heritage of Plato, founder of Neo-Platonism, and theorist of a form of otherworldly spirituality that was profoundly influential in the Western Christian tradition through Augustine. Most influential of all, he sketched a spiritual ascent of the soul's turning inward to discover unity not only with the one Soul and the divine Mind, but with the One itself.