Plato and Parmenides Being

My joy in this research is always highlighted when I find authors who have addressed what I've come to understand through different routes. The way Parmenides speaks about Being is very much like my understanding of All is One or We are One.

The saying that "all roads lead to Rome" makes sense when we realize that "the truth" is "one" and our lives are simply different moments in time before we reach that "truth". We each carry the same "truth" inside but how we each get to it is what is of such great value for our individual selves and what constitutes expressions of life and culture just like all oak trees, might be oaks but each one is equally necessary. 

http://plato.stanford.edu/entries/plato-metaphysics/

Plato's Middle Period Metaphysics and Epistemology

First published Mon Jun 9, 2003; substantive revision Wed Dec 10, 2008

Students of Plato and other ancient philosophers divide philosophy into three parts: Ethics, Epistemology and Metaphysics. While generally accurate and certainly useful for pedagogical purposes, no rigid boundary separates the parts. Ethics, for example, concerns how one ought to live and focuses on pleasure, virtue, and happiness. Since, according to Plato (and Socrates), virtue and happiness require knowledge, e.g., knowledge of goods and evils, Plato's ethics is inseparable from his epistemology. Epistemology is, broadly speaking, the study of what knowledge is and how one comes to have knowledge. Among the many topics included in epistemology are logic, belief, perception, language, science, and knowledge. (‘Science’ derives from the Latin ‘scientia’, which in turn translates the Greek ‘episteme’, from which English derives ‘epistemology’.) Integral to all of these notions is that they (typically) are directed at something. Words refer to something; perception (aesthesis in Greek) involves perceptibles; knowledge requires a known. In this respect, epistemology cannot be investigated without regard to what there is.
Metaphysics, or alternatively ontology, is that branch of philosophy whose special concern is to answer the question ‘What is there?’ These expressions derive from Aristotle, Plato's student. In a collection of his works, the most detailed treatise on the general topic of things that are comes after a treatise on natural things, ta phusika (from which English derives ‘physics’). Since the Greek for ‘after’ is meta, this treatise is titled ‘Metaphysics’. In that work one finds the famous formula that (first) philosophy studies being—the Greek for which is on—qua being. Hence the account of being is ‘ontology’—the English suffix ‘-ology’ signifying ‘study of’: e.g., biology is the study of living things.
Metaphysics, then, studies the ways in which anything that is can be said or thought to be. Leaving to sciences like biology or physics or mathematics or psychology the task of addressing the special ways in which physical things, or living things, or mathematical objects, e.g., numbers, or souls (minds) come to have the peculiar qualities each, respectively, has, the subject-matter of metaphysics are principles common to everything. Perhaps the most general principle is: to be is to be something. Nothing just exists, we might say. This notion implies that each entity/item/thing has at least some one feature or quality or property. Keeping at a general level, we can provisionally distinguish three factors involved when anything is whatever it is: there is that which bears or has the property, often called the ‘subject’, e.g., Socrates, the number three, or my soul; there is the property which is possessed; e.g., being thin, being odd, and being immortal; and there is the manner or way in which the property is tied or connected to the subject. For instance, while Socrates may be accidentally thin, since he can change, that is, gain and lose weight, three cannot fail to be odd nor, if Plato is correct, can the soul fail to be immortal. The metaphysician, then, considers physical or material things as well as immaterial items such as souls, god and numbers in order to study notions like property, subject, change, being essentially or accidentally.

1. The Background to Plato's Metaphysics

Three predecessors heavily influenced Plato's thoughts on metaphysics and epistemology, Heraclitus (c. 540 B.C.-480-70), Parmenides (c.515 B.C.-449-40), and Socrates (470 B.C.-399). Only fragments remain of the writings of Parmenides and Heraclitus, including some contained in the dialogues of Plato. Socrates wrote nothing. Plato's depiction of his teacher is our primary source of evidence for his philosophy. Parmenides argued that there is and could be only one thing, Being. One could not even think or say what is not. Moreover, since change implies that something comes to be what it was not—I change from not being tan to being tan, nothing can change. Reality is static. The appearance of change is just that, a deceptive appearance. Unfortunately, what little we have left of Parmenides does not allow us to decide whether he argued that there is just one item, Being, in his universe—strict numerical monism—or whether there is just one kind of thing, beings or things that are. Parmenides' account of Being seems to have contributed to Plato's doctrine of Forms.
Heraclitus is the apostle of change. For Heraclitus, the ordinary objects of the physical world seem to be continually changing. The only constant, the underlying commonality, is the pattern of change itself. That there are entities that do not change is, for Heraclitus, an illusion. Heraclitus' notion of ‘flux’ seems to have influenced Plato's thinking about ordinary material objects.
In the opinion of most scholars, the seminal influence on all of Plato's thinking was Socrates. However, it appears from the writings of Plato, as well as those of the historian Xenophon and the comic poet Aristophanes, that Socrates was almost exclusively interested in ethics. This is not to say that metaphysical or epistemological issues were of no concern to him. Rather, these sources convey the impression that Socrates was not particularly interested in articulating a metaphysical or epistemological theory (see Vlastos 1991a). Rather, concerned with caring for the soul so that one might live happily (Apology 29d-30b), he uses both epistemological and metaphysical theses in search of answers to his ethical questions. However, it is not easy to distinguish when one is engaged in metaphysical theorizing from when is merely using metaphysical notions. The claim that Socrates was not a metaphysician or epistemologist is particularly hard to evaluate, for we have basically only Plato's dialogues as evidence. Since Plato uses Socrates as a mouthpiece in many of his writings, readers are forced to ask when or whether one is reading the doctrines of Socrates, or Plato, or neither. This ‘Socratic question’ is intimately involved with the question of Plato's development and the chronology of his dialogues.