Many researchers on metaphors in the field of economics have shown interest in the press coverage of economic events; some have included the discourse of textbooks, research articles or businesses in their investigations, and all have underlined frequent references to the economy as a machine or a human being. In this paper, I will endeavour to show how important it is to consider the recurring networks of organic or mechanistic metaphors in connection with theory-constitutive metaphors in economics. The diachronic perspective will show that metaphors can be seen as a reflection of the evolution of economic thinking over centuries, and can thus offer new insight into the field of economics. The heuristic function of metaphor will be discussed at different levelsthose of economic thinkers, ESP teachers and students. I will argue that, as far as terminology is concerned, many a metaphor that is considered as dead is actually just dormant and can be revived at any time to give birth to new metaphors branching out. Metaphors that seem to lose ground, disappear or re-surface, are worth paying attention to as they may reflect a turning point in theory, and spur new approaches to economic problems. In this respect, I will venture to plead for an observatory of metaphors, modelled on neology observatories, with a view to monitoring the emergence of new metaphors. Metaphor could then either be considered as a motor or a barometer of scientific progress and social evolution as well.