At this time the colonial economy of Brazil was in a state of decadence, having exhausted the placer gold of Mato Grosso, Goiás, and, especially, Minas Gerais.

For this reason, the queen Maria I of Portugal, desiring to know more about the central and north of the Brazilian colony, which at that point remained practically unexplored, in order to implement developmental measures, ordered Alexandre Rodrigues Ferreira, as a naturalist, to undertake a "philosophical voyage through the captaincies of Grão-Pará, Rio Negro, Mato Grosso e Cuiabá."

The voyage was undertaken under auspices of the Academy of Sciences in Lisbon, the Ministry of Business and Ultramarine Dominions, and was planned by the Italian naturalist Domenico Vandelli.

He inventoried the flora and fauna, the indigenous communities and their customs, evaluated the economic opportunities and possible places for centers of population.

[2] His "Diary of a Philosophical Voyage" (Diário da Viagem Filosófica) was published in the Revista do Instituto Histórico e Geográfico Brasileiro in 1887.

The Division of Manuscripts of the National Library Foundation preserves in the Alexandre Rodrigues Ferreira Collection hundreds of documents from Philosophical Voyage, along with other papers relating to the Amazon from the 18th century.

In 1794 he was awarded the Order of Christ and took a post as temporary director of the Royal Cabinet of Natural History and the Botanical Garden of the University of Coimbra.

He never resumed work on the species and samples collected in Brazil, nor refined his records and studies of the journey, and much of the material was taken to Paris as war booty.