In particular it contemplates the ancient grandeur of Portugal, and glorifies above all the style of Luís de Camões, the author of Os Lusíadas, and the Portuguese discoveries.

It points to these people and events as ones which Pessoa believed could regenerate, or return Portugal to its past greatness.

However a friend of Pessoa convinced him that "Mensagem" would be a more appropriate title as "Portugal" had already been widely used with common products.

Pessoa liked the word "mensagem" because of the expression in Latin: Mens agitat molem, meaning, "the spirit moves matter" a phrase from the epic poem The Aeneid by Vergil, said by Anchises when he was explaining the Universe to Aeneas.

According to a letter dated to 13 January 1935 to Adolfo Casais Monteiro, Mensagem was the first book that Pessoa was able to complete.