It is often said that people have the right to hold whatever beliefs they want, even if they fly in the face of fact. To what extent is this true? There is surely no serious problem with a person believing that tulips are hallucinogenic (the worst case scenario is that they will be disappointed), but there is surely something wrong with a parent believing that large doses of arsenic is an integral part of a healthy child's diet. Is harm really the only factor that matters? Do people have a duty to hold true opinions if they are able to do so? Do people have the right to try and correct the false beliefs of others?