The article explains the so-called 'omni-insular' theory based on the donation of Constantine. We conclude that the references to this Donation are few and circumstantial. Just in some cases can be testified that the Pope demanded an economical and periodical amount based on his rights over the whole Occident islands. This amount seems derived from the feudal context, the prestige of being the successor of Peter, and the recognition of apostolic protection. The intervention of the popes in the Portuguese and Castilian overseas expansion was based firstly on their condition of Vicar of Christ (apostolic authority) and secondly on the hierocratic doctrine of the Lordship of the World (Dominium Mundi).