Oneness in the Early Greek Philosophy
The early Greek philosophers were contemporaries of Lao-tzu. The Principle of Oneness is scattered in many fragments of the early Greek philosophy. Once the Principle is recognized, the Principle can be identified systematically in the early Greek philosophy. The Greek philosophy positively supports our interpretation of the Tao Te Ching in terms of the Principle of Oneness.
We shall show how the Principle of Oneness appears in the ancient Greek philosophies of Parmenides and Heraclitus, as examples.
Parmenides (born about 515 bc), in his On Nature, argued that reality must be based on something "that is there" ( the What-is-there, or the actual modes that can be thought of). What-is-there is a reality with Oneness. Parmenides holds that conventional objects are often perceived by mortals to exist, but they have no real existence. He recognizes reality at two levels as his doctrine of two truths: (1) the heart of well-rounded Truth and (2) the Opinions of Mortals. The well-rounded truth are the actual modes (the Being) that retain Oneness implicitly; the Opinions of Mortals are based on the conventional objects with explicit inter-relationships to preserve Oneness. In many interpretations, the Opinions of Mortals is mistaken as an invalid way to search for truth. Parmenides is credited with his concept of Being; his view of the opinions of mortals as a way of Becoming is often ignored.
Heraclitus (535- 475 BCE.) is the first Western philosopher to state that human nature is subject to the same law of nature as the cosmos. He proclaims the logos, the universal principle through which all things are interrelated and all natural events occur. The logos is the underlying order that connects the opposites to preserve Oneness. The world exists as a coherent system of Oneness, in which a change in one direction is always coupled with a corresponding change in another. At the conventional level, all things are in a state of continuous flux; stability is an illusion. Only change and the law of change, or Logos, are real. The Logos is a representation of Oneness as the laws of nature. At the conventional level, our own private understandings of the Logos may also be true. Heraclitus also has two ways to understand the law of the universe: the Way of the Logos and the Way of Opinions. He emphasizes the unity of opposites in the process commonly known as Becoming.
Plato Theory of the Good
Plato's Theory of Ideals and Theory of the Good may be related to the Principle of Oneness.