The Greek philosophers were concerned to explain the nature of things and also tried to explain human own nature.
This is the most famous saying of the sophist and rhetorician Greek philosopher Protagoras, born in Abdera, in Thrace, (485 B.C.-411.B.C. approximately).
This sentence completes the philosophical rationalization process that took place in the ancient Greece. Although this view may is too brief and topical, it’s worthy to remember how they went from a religious-mythical first stage in which the center of thought used the relationship with the gods as an explanation to things, to the philosophical phase as a way to explain the physical nature and its phenomena and finally to the anthropocentric stage concerned to the man himself.
This saying expresses the change in the study object for the Greek rationalism: Now, without leaving the interest about the natural phenomena, the center is the man and all his complexity. This is what the saying "Homo omnium rerum mesura est" (“Man is the measure of all things”) summarizes.
Indeed Diogenes Laertius tells us that the whole Greek sentence, of course, was: “πάντων χρημάτων μέτρον ἔστὶν ἄνθρωπος, τῶν δὲ μὲν οντῶν ὡς ἔστιν, τῶν δὲ οὐκ ὄντων ὠς οὐκ ἔστιν” = "Man is the measure of all things: things which are, that they are, and things which are not, that they are not".
The exact meaning of the sentence is a matter of discussion, as it could not be otherwise in the case of philosophers: does it refer to the man as an individual being, which would set absolute relativism, or to the man as a group being?; With "all things" it also refers to the essence of intangible things or only to those involving assessments by men?
Already in Antiquity itself there was criticism of this principle, dissatisfied with the relativism that introduced in the analysis of things. Plato, for example, refers critically in several of his dialogues to Protagoras and his sentence, so in Cratillo 386a or in Theaetetus 152a; he says in Laws 716c::
In our eyes God will be “the measure of all things” in the highest degree—a degree much higher than is any “man” they talk of
ὁ δὴ θεὸς ἡμῖν πάντων χρημάτων μέτρον ἂν εἴη μάλιστα, καὶ πολὺ μᾶλλον ἤ πού τις, ὥς φασιν, ἄνθρωπος:
As long as we are men ourselves, I invite all of us to reflect about it and find the value and personal meaning for such a historical and successful sentence.
Obviously the Greek people are at the source of all our culture.