A Positio is a formal brief arguing for the canonization of an individual in the Roman Catholic Church. Before canonization, the formal declaration by the Pope that a person is a saint, there is a long process, with various intermediate steps. First, a person whose holiness is being investigated (by a Postulator, appointed by the Pope) is referred to as a Servant of God. The very fact of appointing a postulator means that the process of beatification has been activated.
If investigations reveal that the person was indeed holy enough, then a "formal argument for sainthood", the positio, is presented to the Congregation for the Causes of Saints. This document contains the informatio, or life story, of the Servant of God under investigation, as well as a series of documents and testimonies to support the cause (summarium). If the Positio is approved, the Pope bestows the title of “Venerable,” that is, worthy of the devotion of Catholic believers.