Orthesis belonged to the kamaldulensiska monastic order. He was probably the first one, according to Adam Ferguson, who used the term "economics" of the science, in which he exercised a remarkable activity, particularly by Economia Nazionale (1774) and Riflessioni sulla popolazione (1790), which along with other his works reprinted in Pietro Custodis anthologies "Scrittori classici italiani di economia politica" (1802–16). He was against mercantilism.
He anticipated certain aspects of Adam Smith and Thomas Robert Malthus, especially the latter, as he felt that the population propagation, if it were offered free rein, would take place in a geometric progression with a doubling every 30 years. No one knows exactly how he died.