Sachs divides early dances into 'Imageless dances' and 'Image dances'. By 'imageless dances' he meant dances which have no set form, but aim at getting the dancers into a state of ecstasy. In this state the dancer(s) seem changed, in a trance, and are often thought of (by their society) as being 'possessed by spirits'. These dances are done on certain occasions: marriage, war, famine, illness or death, and so on. They are found in all early ('primitive') societies.