Kant's Groundwork of the Metaphysics of Morals critiques moral sentiment. He attempts to demonstrate that morality is based on an intellectual rather than emotional faculty.
Kant does not view the end of morality as happiness, but rather he phrases it as worthiness to be happy. In other words, happiness is the product of action and cannot retroactively be the grounds of legitimacy for that action. While initially this may appear confusing, because typically it is thought that we pursue actions with the goal of happiness in mind, Kant urges us to treat others as an end in themselves and not as a means to an end. In other words, the goal of morality is the other, or respect for the autonomy of the other.
Happiness is not the relevant criteria for judging the moral validity or worth of an action. Instead, Kant conceives the categorical imperative as the basis upon which individuals can determine principles of moral action. The universalizing character of the categorical imperative implies meta-principles of equality and autonomy.
Autonomy (auto- "self" + nomos, "law") is possible through the categorical imperative as individuals are required to theorize their actions as laws. Kant believes that laws themselves provide sufficient motivation for action. The ability to live and act according to such laws demonstrates the possibility of freedom through a rational mind.
The categorical imperative has the structure of law and a necessary implication is that laws are required to be applied equally in order to be considered as legitimate laws. The criteria of justice and fairness as arbiters of equality are therefore a necessary part of moral reasoning. Legal Positivists attempt to defer the question of legitimacy to the people that are governed by the laws. They write that as long as there are people that obey or habits of obedience, the laws are legitimate. But this only begs the question as to the relevant criterion of legitimacy for the people....