Marchant was born at Couvin in what is now Belgium in 1585 and entered the recollect community in that town in 1601, aged 16.

[1] He acquired a profound knowledge of scholastic philosophy and theology, and for several years taught in the schools of his order.

In 1639 Marchant was appointed commissary general over the provinces of Germany, Belgium, the Netherlands, England, Scotland, and Ireland.

[1] His duties as commissary general brought him into contact with Irish politics during the times of the Confederation of Kilkenny.

He was called upon by the authorities of the order to justify his conduct in connection with the Irish question, and in 1661 he addressed to the general chapter then assembled in Rome his apologia under the title of Relatio veridica et sincera status Provinciae Hiberniae.