Paternalism is the use of coercion to force people to do or refrain from something against their will for their own good. Liberals of all stripes generally reject paternalism for reasons most lucidly laid out in J.S. Mill’s masterpiece On Liberty. First, we assume the individual is the best judge of her own good. Second, whether or not the individual is the best judge of her own good, we rightly doubt that another individual (or assembly thereof) has the legitimate moral authority to substitute their judgment for the individual’s by force — especially in light of widespread disagreement about the nature of a good life. Third, truth is hard to come by, and none of us can be fully certain we’ve pinned it down. Allowing people to act on diverse opinions about morality (or rationality) broadens the search for truth about good lives by setting up a decentralized system of social laboratories where experiments in living succeed or fail in plain view. So, unless an action harms somebody else, people should be at liberty to satisfy their preferences, whether saintly or sinful, coolly rational or impulsively emotional.