Aristotle 
Nicomachean Ethics 

One of the most important philosophical works in history, a work that has had tremendous influence on philosophy, literature, and psychology, and has helped lay the foundations of the modern day intellectual landscape. The influence of 'The Nicomachean Ethics’ is still visible in the works of philosophers of the 21st century, such as Martha Nussbaum and Alasdair Mac Intyre. With remarkable lucidity, Aristotle tackles the question of the nature of happiness, and that of moral and intellectual virtues. He aims to prove that both are linked to and indivisible from one another that virtuous behaviour is necessary if happiness is to be obtained and from this he maps out the steps to follow and the requirements to achieve it. In short, 'The Nicomachean Ethics’ sketches out a hierarchy of virtues to find the highest good a human can accomplish, which in turn will lead them to true happiness.