 Because the concept of negative freedom concentrates on the external sphere in which individuals interact, it seems to provide a better guarantee against the dangers of paternalism and authoritarianism perceived by Berlin. To promote negative freedom is to promote the existence of a sphere of action within which the individual is sovereign, and within which she can pursue her own projects subject only to the constraint that she respect the spheres of others. Humboldt and Mill, both advocates of negative freedom, compared the development of an individual to that of a plant: individuals, like plants, must be allowed to grow, in the sense of developing their own faculties to the full and according to their own inner logic. Personal growth is something that cannot be imposed from without, but must come from within the individual.