Philosophers define objective morality by its universality, believing that some moral ideas are so fundamentally important that everyone should follow them. Immanuel Kant, in 1785, stated that in order to be considered an objective moral law, a moral ideal must be universal and must never treat humanity as a means to an end, and that the world should accept the ideal as a universal law.
As opposed to the ideal of universal morality, personal choice determines subjective morality. The idea is that each individual has the right to choose specific moral ideals by which to live her life. Subjective morality also suggests that no one has the right to demand that others adhere to the same ethical ideals as they do. For instance, you may believe that you have a moral responsibility to vote in public elections; however, this feeling does not mean that you believe that everyone has a moral responsibility to vote in public elections or that society should mandate voting.
Theorists disagree about the origins of objective morality. Theologists believe that you define objective morality by interpreting religious decrees. Philosophers contend that objective morality is the result of careful metaphysical thought, and the development of specific rules by which you can justify moral ideas as universal. The role of metaphysics is for philosophers to define specific laws by which individuals test moral ideals in order to determine if those ideals are objective.
Subjective morality theories argue that all morality is situational and that even the decision to be moral represents a conditional choice. Situational morality suggests that you consider every moral action independent of objective morals or prior events, evaluating each situation based on the conditions of the choice. As a result, the decision to make moral choices becomes a moral choice in itself; subjective moralists argue that this decision has its own value. For instance, if you decide to accept that you have a moral responsibility to vote in an upcoming election, you are making two decisions. The first is your decision to accept the moral ideal and the second is that you must go vote in order to follow your ideal.