What role does happiness play in ethics? Explain with reference to Kant and Aristotle.
Before I answer this question, I should clarify that "happiness" was not the same thing for Aristotle and for Kant, and it's yet another thing for us; this has something to do with the different languages and the different time periods. The Greek word which is translated as "happiness" is "eudaimonia." This means, more accurately, "well-being" or "flourishing." It has nothing to do with subjective contentment. You might be "happy" watching TV, but Aristotle would not call this "eudaimonia." Kant, on the other hand, describes happiness (Glück) as continuous well-being, enjoyment of life, and complete satisfaction with one's condition. So Kantian happiness is much more subjective that Aristotelian happiness (and closer to what we often mean by "happiness"). Now that the terminological issue has been addressed, let's turn to the main question: what role does happiness play in Aristotle's and Kant's ethics?
For Aristotle, happiness was the highest end and the goal of human life. The Nicomachean Ethics begins by asserting that all arts and all crafts have one end, and we later learn that this end is happiness. Aristotle's ethics are often described as "eudaimonistic." Of course, happiness in this context entailed the cultivation of moral and intellectual virtues and required that even one's descendants be virtuous, since a person cannot be deemed "happy" until well after he or she is dead.
Kant, on the other hand, did not have much room for happiness in his ethics. Kant's ethics are often described as "deontological" or duty-based. For Kant, the right action was that which we ought to do irrespective of how it makes us feel. Our happiness is entirely secondary and has nothing to do with morality.
Here, I should also clarify that Aristotle's ethics deal with the question of how one should be whereas Kant's ethics deal with the question of how one should act. Aristotle's conclusion is that one should lead a life of happiness (eudaimonia) and Kant concludes that one should act according to duty irrespective of how happy it makes us.