Discusses the epistemology of historical knowledge by clarifying the relationship between the present and the past and argues that only the present can be known; the past is mirrored through the present. The historian's work consists not of gaining knowledge of the past but of what can be perceived in the present as past. The historian cannot know anything of pasts that are no longer present, no matter what sources are available. The object of study is therefore not the pure and uncontaminated past but that which is still present in the here and now. History is therefore always a construction, rather than a reconstruction, that selects out facts in terms of the questions posed from sources existing in the present. Understanding is possible because the historical practitioner makes meaningful connections between facts on the basis of his theoretical assumptions. According to German historian Johann Gustav Droysen (1808-84), the goal of historical research is to understand what is left of the past in light of the present.