19th-century European theologians also considered Ancient Egyptian religion to contain pantheistic elements and pointed to Egyptian philosophy as a source of Greek Pantheism. The latter included some of the Presocratics, such as Heraclitus and Anaximander. The Stoics were pantheists, beginning with Zeno of Citium and culminating in the emperor-philosopher Marcus Aurelius. During the pre-Christian Roman Empire, Stoicism was one of the three dominant schools of philosophy, along with Epicureanism and Neoplatonism. The early Taoism of Laozi and Zhuangzi is also sometimes considered pantheistic, although it could be more similar to Panentheism.