Greek Philosophy. It was Pythagoras (ca. 582 - 504 BC) who gave Philosophy its name, "the love of wisdom". Presocratic Philosophers were the first Greek philosophers of the Western tradition. Their most well-known successors were Socrates, who introduced the Maieutics; his pupil Plato, who believed reason was the key to knowledge and became a notable teacher in the Academy, and Aristotle, who believed that experience was the best way to gain knowledge. Aristotle eventually founded the Lyceum. Socrates, through Plato, influenced much of Christian theological thought and formed much of medieval philosophy. His concept of the soul and the importance of cultivating it, is central to understanding Western Culture. 
Aristotle said that Thales was the first to consider the basic principles and the question of the originating substances of matter and, therefore, the founder of the school of natural philosophy.
- Greek philosophers were among the first in the West to explore nature in a rational way and to make educated guesses about the creation of the world and the universe. This is why Greece is often referred to as the birthplace of Western culture. 
At the closing period of Greek philosophy Neoplatonism was founded by Plotinus of Lycopolis; its emphasis is a scientific philosophy of religion, in which the doctrine of Plato is fused with the most important elements in the Aristotelian and Stoic systems.
Western culture is the heir of the Greek Philosophy that came to our society through the ideals and works of the Hellenistic philosophers, the medieval Muslim philosophers, the European Renaissance and the Enlightenment.
Theophrastos (371 – c. 287 BC) was the first to writer about the Greek philosophy.
Nothing is more active than thought, for it travels over the universe, and nothing is stronger than necessity for all must submit to it. Thales.
Which is not, is not. The appearance of movement and the existence of objects, states of affairs and so on, are mere illusions; they only seem to exist; multiplicity is unreal. Parmenides of Elea.
Choose rather to be strong of soul than strong of body. Pythagoras
The gods have not revealed all things to men from the beginning, but by seeking they find in time what is better. Xenophanes.
As for me, all I know is that I know nothing. Socrates.
All the gold which is under or upon the earth is not enough to give in exchange for virtue. Plato.
Democracy arises out of the notion that those who are equal in any respect are equal in all respects; because men are equally free, they claim to be absolutely equal.
Far best is he who knows all things himself;
Good, he that hearkens when men counsel right;
But he who neither knows, nor lays to heart
Another's wisdom, is a useless wight. Aristotle.
My view is, to sum it all up, that all things are differentiations of the same thing, and are the same thing. And this is obvious; for, if the things which are now in this world—earth, and water, and air and fire, and the other things which we see existing in this world—if any one of these things, I say, were different from any other, different, that is, by having a substance peculiar to itself; and if it were not the same thing that is often changed and differentiated, then things could not in any way mix with one another, nor could they do one another good or harm. Neither could a plant grow out of the earth, nor any animal nor anything else come into being unless things were composed in such a way as to be the same. But all these things arise from the same thing; they are differentiated and take different forms at different times, and return again to the same thing. Diogenes.
God is not separate from the world; He is the soul of the world, and each of us contains a part of the Divine Fire. All things are parts of one single system, which is called Nature; the individual life is good when it is in harmony with Nature. In one sense, every life is in harmony with Nature, since it is such as Nature’s laws have caused it to be; but in another sense a human life is only in harmony with Nature when the individual will is directed to ends which are among those of Nature. Virtue consists in a will which is in agreement with Nature. Zeno
Not what we have but what we enjoy, constitutes our abundance. Epicurus