In this artwork, how is the Subject matter discussed?
The painting has long been thought to be a portrait of an Amsterdam mayor. It was listed thusly in the collection of the Duke of Orléans at the Palais Royal of Paris in 1727.However, the painting depicts the preacher Eleazar Swalmius, who was born in Rhoon, but operated in Amsterdam. 
Rembrandt painted this portrait in 1637, when the pastor was about 55 years old. Swalmius was born in Rhoon to Hendrick van de Swalme, or Henricus Swalmius. Hendrick van de Swalme's family was probably originally from Flanders. His father spent time in England before becoming a preacher in the late 16th century. Like his father, Eleazar became a preacher too (Counter-Remostrant).Swalmius was active as a pastor in Poortugaal and Hoogvliet near Rotterdam since 1605 and in Schiedam between 1612 and 1622. In 1622 he settled in Amsterdam, where he would live up to his death, and be buried in the Oude Kerk in 1652. The Van der Swalme family must have known Rembrandt well. Carel, a brother of Eleazer and "dike count" (dijkgraaf) of Oranjepolder, for example, witnessed the drawing up of the will of Rembrandt van Rijn and Saskia van Uylenburgh.
Counter-Remostrant Saskia van Uylenburgh Rhoon Rembrandt Duke of Orléans dijkgraaf Eleazar Swalmius