[eng] In the present research we propose the need for prior researchon the phenomenological nature of money to carry out a clarifcation ofthe concepts that historical sciences (in this case, the history of economics)often project from the study of the sources. After showing the need for adistinction at the transcendental level between money as an entity that is«to buy» or as an entity that is «to pay», it will be shown how theestablishment of this distinction could be fertile for methodologicaldiscussions. The example will be the scope and interpretation of the«Greek Law on Sale» by Fritz Pringsheim.