The practical application of philosophy was a major concern expressed by al-Farabi in many of his works, and while the majority of his philosophical output has been influenced by Aristotelian thought, his practical philosophy was unmistakably based on that of Plato. In a similar manner to Plato's Republic, al-Farabi emphasized that philosophy was both a theoretical and practical discipline; labeling those philosophers who do not apply their erudition to practical pursuits as "futile philosophers". The ideal society, he wrote, is one directed towards the realization of "true happiness" (which can be taken to mean philosophical enlightenment) and as such, the ideal philosopher must hone all the necessary arts of rhetoric and poetics to communicate abstract truths to the ordinary people, as well as having achieved enlightenment himself. Al-Farabi compared the philosopher's role in relation to society with a physician in relation to the body; the body's health is affected by the "balance of its humours " just as the city is determined by the moral habits of its people. The philosopher's duty, he wrote, was to establish a "virtuous" society by healing the souls of the people, establishing justice and guiding them towards "true happiness".