Since habitual residence is a test of fact, it cannot be a purely legal concept and there are different views about the factual situations which it is supposed to denote. Some authors believe that the sole criterion that the test of habitual residence should be purely objective, seeking evidence of physical presence over a considerable period of time. Others assert that the test should be both objective and subjective elements: the "factum" or physical presence in a given place and the "animus" to continue to stay there.