Ethics is the most important focus of Stoic philosophy which aims at bringing into the individual human soul, the peace and harmony, order and beauty, regularity and constancy that is apparent in the cosmos. This perfect state is achieved through apatheia or apathy which is perfect passionless-ness.
Zeno had earlier been influenced by the Cynics, whose principle was live according to nature. Life according to nature, became also the aim of Stoicism. However, the meaning given to these words was entirely different. For the Cynics, like Diogenes of Sinope, life according to nature, was life according to senses and instincts. For the Stoics, living according to nature meant life according to reason. So, whereas the Cynics seem to have thought of animal “nature”, the Stoics referred to human nature. Whereas the Cynics thought of natural as opposed to artificial and conventional, the Stoics thought of natural as rational.