[4] Seys chose to work as a Methodist reverend (preacher in 1825 and ordained minister in 1829),[4][5] and his family disinherited him for it.

[5] Following the death of his predecessor, Beveridge Cox, Seys led the Methodist mission in Liberia for ten years until poor health forced him to resign in 1844.

[5] From 1858 to 1862, Seys acted as a United States government agent[4] helping the freed passengers of slave ships captured by the U.S. Navy, having responsibility for up to four thousand men, women and children at a time.

[1][9][13] In this position, Seys faced many obstacles due to the lack of funds coming from the United States.

In a February 11, 1871, report to the U.S. House of Representatives, Representative Thomas Swann from the United States House Committee on Foreign Affairs stated that Seys "charges salary for sixty days, and also for fifty-eight days, transit in returning to his post, and for the services of W.A.