The earmark of liberalism, or liberal political theory, is that some conception of liberty has priority as a political value (say, over equality). Some liberal political theories, or liberalisms, are founded upon ethical theories or theories of the good life that are, in democratic societies where persons need not agree on moral or religious issues, controversial as justifications for laws and state policies.
For example, imagine a proposed law to ban the sale of caffeinated beverages on the grounds that drinking caffeine is not conducive to a person’s prospects for long-term health. One who endorses this reason for the caffeine ban might claim that health is an objective good and so is integral to an ideal or perfect human life. If so, the caffeine ban leads to more healthy persons in society and enables persons to live more ideal or perfect lives. Although perhaps intuitively appealing, this justification for the hypothetical ban on caffeinated beverages depends on or presupposes ethical, and a form of perfectionist, values that persons in a democratic society can reasonably disagree on. Moreover, many contemporary liberal political theories argue that states should neutrally justify laws and policies with reference to reasons that persons who hold diverse, and maybe incompatible, ethical values and conceptions of the good life can share and accept.