Petrus was born in Amsterdam on 13 September 1526, the son of Pieter van Opmeer and Maria van Akersloot. Throughout his life, he demonstrated a great love of learning and had the family resources to pursue his interests. He was educated in Amsterdam at the school run by
Alard van Amsterdam and
Nicolaas Cannius, spent time in
Leuven, then went to
Tournai to learn French and mathematics. At the age of 19, he married Sophia Sasbout, and went to
Delft to study Greek with Petrus Resenius, rector of the
Latin school. He was studying
civil and canon law at
Leuven University when the
Dutch Revolt broke out, prompting him to switch to theology. After the murder of
Cornelis Musius, Opmeer offered his services to the
Army of Flanders and was appointed secretary to the Council of War by
Francisco de Valdez. After the
Siege of Leiden, he returned to his native Amsterdam, until the city was lost to the
rebels in 1578 and Catholic worship was prohibited. He then moved to Delft and lived there the rest of his life, dying on 4 November 1594, and being buried in the
Oude Kerk. His son, Petrus Opmeer the Younger, published a number of his writings posthumously. ==Writings==