The above quote was taken from Aristotle's Nicomachean Ethics written in 350 B.C.E. about human nature. The quote can be found in Book IV, which discusses the value of friendship

The majority of Aristotle's training came from the School of Athens, where he was mentored by Plato. (The picture below depicts Aristotle, on the right, with Plato). When Plato died Aristotle was not appointed head of the school so he returned to Macedonia to tutor Alexander the Great. Aristotle then went back to Athens and set up a school called the Lyceum. After the death of Alexander the Great, Athens rebelled against Macedonian rule. Aristotle decided it would be safest to flee to the island of Euboea. He died soon after.

Aristotle was an intellectual who wrote about all human knowledge as it was known in his time. His writings mainly fell into two categories: philosophical and scientific. He wrote many books throughout his lifetime including Athenian Constitution, Economics, and Virtue and Vices. Western civilization was called Aristotelian until the end of the 17th century.