During the nineteenth century, positivists charged that since historical accounts did not uncover the laws involved in human behavior, they were devoid of significance and should be replaced by sociological studies. Theorists, including Droysen, responded that man has a dual nature. Man's biological self is the inalterable substance of his life, while his spiritual self enables him to create its form. The objects of this creation, social institutions, embody the ideas and ideals of a social order and are transformed when these values change. Remnants of the past are always contained within the new order and thus history both records the past and is embraced by the present. Since man is responsible for his progress he must know the past in order to fully understand and to act in the present. Droysen called this understanding of history Verstehen.