Every effort to deal with the history of ideas is beset by hazards. Semantic traps are strewn along the way of the inquirer; such words as democracy, liberty, justice, etc., point to different concepts or varying complexes of concepts as they are used in different periods of history and by different men. The unuttered and frequently unacknowledged presuppositions of those who employ them also vary; and since meaning largely depends on context the difficulties of understanding what is meant are increased by the difficulty of ascertaining what is at the back of the minds.