Thirty years after its demolition, the House in Jean Mermoz (Fabio Cruz Prieto, 1956-1961), a foundational work of the Valparaiso School, regains substance thanks to a design investigation with the aim of recovering the invaluable experience of being on site. However, what was recreated in 2021 was not strictly a replica but rather what was never seen of the house: the formwork system of the concrete structure. In light of the paradox of replacement by Heraclitus and Plato, and Aristotle's causes, two referential cases are analyzed-the Ise Shrine (7th century) and the Barcelona Pavilion (1929). This raises the need for a fifth cause; the contextual one. Finally, the article presents a critical reflection on the case of the recreation of the House in Jean Mermoz within the issue of architectural reconstructions.