Are we responsible for making bad decisions or doing evil? How do we know right from wrong? What tells us that we are following the "Doctrine of the Mean" between the extremes of too much or too little? Socrates said that no one knowingly commits evil, but Aristotle decided to elaborate on this.
[I borrowed this image from Freud regarding the Id, Ego and Superego. However, I think it is just an expansion onto Aristotle's own ideas]
Aristotle tells us that wisdom is the product of practical knowledge and intuition. We learn practical knowledge (phonesis) from our parents or the state. Without phonesis it is impossible to know how to pursue the correct ends. Intuition is something we develop by putting our moral compass into practice and using it everyday.
Aristotle elaborates that every action should be considered as either voluntary or involuntary and we should only recognize voluntary actions as truly virtuous or lacking virtue. Involuntary actions are done under duress, compulsion or ignorance and can not be considered representative of character. Can a person be called brave if he is forced to fight? Can a person be called a coward if he runs away from a sudden noise?
Voluntary action requires reason; the balance between appetite and seeking the higher good. No one knowingly does evil but we are responsible for our ignorance (i.e. not knowing the consequences of our actions). If we choose to remain ignorant then we are committing evil. These statements by Aristotle seem to predict the development of existentialism in which our free will is the primary agent controlling our life. Aristotle calls knowing what is right but not doing it akrasia or a lack of self-control. This is the worst vice since the person is beyond reason; he has abandoned reason and surrendered control to his lower, baser appetites. However, if you lack self-control because of temperament (emotion) that is better than if you are conscious about your [bad] choice.
Aristotle also adds that being virtuous requires practice and habit. Being good is not enough, you must practice being good. Aristotle states that the winner of the Olympics is not the strongest man, but the strongest man who competes.