Athenian democracy developed around the fifth century BC in the Greek city-state (known as a polis) of Athens, comprising the city of Athens and the surrounding territory of Attica, and is the first known democracy in the world. It was a system of direct democracy, in which participating citizens voted directly on legislation and executive bills. Participation was not open to all residents: to vote one had to be an adult, male citizen who owned land and was not a slave, and the number of these "varied between 30,000 and 50,000 out of a total population of around 250,000 to 300,000."
The Classical Athenian Democracy by 
Essentials of Comparative Politics by 
Constitution of Athens and Related Texts by 
The Origins of Democratic Thinking by 
The Cambridge History of Greek and Roman Political Thought by Cleisthenes is credited with the reformation of the constitution of Ancient Athens and setting it on a democratic footing. He is considered the "Father of Athenian Democracy."
Aristotle was an ancient Greek philosopher and scientist. At seventeen or eighteen years of age, he joined Plato's Academy in Athens and remained there until the age of thirty-seven (c. 347 BC). His writings constitute the first comprehensive system of Western philosophy. Shortly after Plato died, Aristotle left Athens and, at the request of Philip of Macedon, tutored Alexander the Great beginning in 343 BC.
Socrates was a classical Greek (Athenian) philosopher credited as one of the founders of Western philosophy. He is an enigmatic figure known chiefly through the accounts of classical writers, especially the writings of his students Plato and Xenophon and the plays of his contemporary Aristophanes.
Routledge Philosophy Guidebook to Plato and the Trial of Socrates by Plato was a philosopher in Classical Greece and the founder of the Academy in Athens, the first institution of higher learning in the Western world. He is widely considered the most pivotal figure in the development of philosophy, especially the Western tradition. Unlike nearly all of his philosophical contemporaries, Plato's entire work is believed to have survived intact for over 2,400 years. Along with his teacher, Socrates, and his most famous student, Aristotle, Plato laid the very foundations of Western philosophy and science.
Plato and the Republic by Xenophon of Athens was an ancient Greek philosopher, historian, soldier and mercenary, and a student of Socrates. As a historian, Xenophon is known for recording the history of his contemporary time, the late-5th and early-4th centuries BC, such as the "Hellenica", about the final seven years and the aftermath of the Peloponnesian War (431–404 BC).
Thucydides was a Athenian historian and general. His "History of the Peloponnesian War" recounts the 5th century BC war between Sparta and Athens to the year 411 BC. Thucydides has been dubbed the father of "scientific history" because of his strict standards of evidence-gathering and analysis of cause and effect without reference to intervention by the gods, as outlined in his introduction to his work.
