Circulation refers to the movement and ongoing use of currency within an economy, including physical money and specific bank deposits. However, authors have extended this idea metaphorically, associating it with the movement of people, ideas, and resources. Stephen Graham compared the vitality of society to circulation, likening it to the flow of blood in living organisms, while Rudyard Kipling portrayed traffic as a symbol of dynamic economic and social energy.
Likewise, Ernst Haeckel drew comparisons between state transportation systems and biological circulatory systems. These viewpoints highlight circulation not only as a financial process but also as a metaphor for interconnected life processes, linking economic systems with the patterns of human and natural activity.