Thirty years after its demolition, the House in Jean Mermoz (Fabio Cruz Prieto, 1956-1961), a foundational work of the Valparaíso 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.