Parmenides was native of Elea, in southern Italy. His date is uncertain but it is said that young Socrates met him when Parmenides was 65 years of age. This makes his birth around 515 BCE. He was the founder of the Eleatic school of philosophy.The southern Italian & Sicilian philosophy was more related to mysticism unlike the Ionian philosophy which was scientific and skeptical in nature. Mathematics, under the influence of Pythagoras, flourished in Magna Gracie in southern Italy and was entangled with mysticism and was not scientific as it is today.
Parmenides was influenced by Pythagoras but the extent to this influence is conjectural. Parmenides is historically important as he is considered to be inventor of Logic but what he really invented was metaphysics based on Logic.
His doctrine is divided into two parts “the way of truth” and the “the way of opinion”. The Way of Truth discusses that which is real, which contrasts in some way with the argument of the Way of Opinion, which discusses that which is illusory. In his poem ‘In Nature’ he illustrates his doctrine .He considered the senses deceptive, and condemned the multitude of sensible things as mere illusion. The only true being is “the One” which is infinite and indivisible. It is not, as in Heraclitus, a union of opposites, since there are no opposites. He apparently thought for instance, “Cold” means only “not Hot”, and “Dark” means only “not light”. “The One” of Parmenides is different from “The God” we conceive because Parmenides considered the one as a material and extended, for he speaks of it as a sphere present everywhere, encompassing everything hence indivisible and indestructible. Heraclitus maintained that everything changes; Parmenides retorted that nothing changes. The essentials of his teaching as follow:
“Thou canst not know what is not-that is impossible-nor utter it; for it is the same thing that can be thought and that can be”
“How, then, can what is be going to be in future? Or how could it come into being? If it came into being, it is not, nor is it if it is going to be in the future. Thus is becoming extinguished and passing away not to be heard of."
"The thing that can be thought and that for the sake of which the thought exists is the same; for you cannot find thought without something that is, as to which it is uttered.”
Bertrand Russell explains this argument as:
“When you think you think of something; when you use a name, it must be the name of something. Therefore both thought and language requires objects outside themselves. And since you can think of a thing or speak of it at one time as well as at another, whatever can be thought of or spoken of must exist at all the time. Consequently there can be no change, since change consists in things coming into being or ceasing to be”
Parmenides contends that, since we know what is commonly regarded as past, it cannot be really be past, but must, in some sense , exist now. Hence he infers that there is no such thing as change.