Legal history is the study of how law has evolved over time, and why it has evolved. Legal history parallels the development of civilisations, and is a component of social history. Legal historians record the evolution of laws and provide an analysis of how these laws evolved, so that the origins of various legal concepts can be better understood. Some consider legal history to be a branch of intellectual history. Twentieth century historians assess in a more contextualised manner, much like social historians, viewing legal institutions as complex systems of rules, participants and symbols that have interacted with society to promote changes in certain aspects of civil society.