The Dutch term is schepen, which refers to a municipal office that existed in the Netherlands from the 1200's until the Napoleonic system was introduced in the early 1800's. Sewel's 1735 dictionary says "SCHEPEN - a Magistrate, somewhat like a Justice or Alderman". The word schepen comes from the Old Saxon scepino (judge) and is related to the German Schöffe (lay magistrate).

Those who write in English about Leeuwenhoek often translate it as alderman, which implies the administrative duties that these officials originally had. Others translate it as magistrate, which implies the judicial duties that these officials retained after the city's mayors took over their major administrative duties. These officials were also members of the Heeren van de Wet (gentlemen of the law), a group of councillors made up of the sheriff, the five mayors, the seven magistrates, the pensionary, and the two city secretaries (schout, burgemeesteren, schepenen, pensionaris, secretarissen).

The 1660 appointment of Leeuwenhoek as camerbewaarder noted that he was appointed by "H.H. Schout, Schepens ende die van de wet". Dobell translated this (p. 32) "Chief Judge the Sheriffs and the Law Officers". Unfortunately, that plural Sheriffs includes both the actual sheriff and the magistrates. Thus, many accounts of Leeuwenhoek's life in English say something similar to "He was made chamberlain (camerbewaarder) to the sheriffs of Delft" (Eye of the Beholder p. 112).

By the time Leeuwenhoek became involved in Delft's government, the magistrates had long since lost their major administrative duties. They still functioned as councillors when they met with the other Heeren van de Web. However, the records show that they primarily functioned as a municipal court would today. Once a week, they met in their own room, the Schepenenkamer.

Twice a week, they held court in the Burger Zaal, the largest indoor area in the Stadhuis. They sat in a separate raised area called the Vierschaar to make announcements of their activities and decisions. It is unclear whether Leeuwenhoek played any role in these proceedings.

Boitet lists over twenty-two hundred magistrates beginning with Jan Spyke in 1300. In Leeuwenhoek's day, Delft had seven of them at a time.

With one exception, all of Leeuwenhoek's relatives who were on the Veertigraad also served as magistrate, often multiple times. During the time Leeuwenhoek was kamerbewaarder, Jacob Cornelis Hogenhouck and Maarten Pieters Hogenhouck served as magistrates.

The terracotta of the magistrates (above) comes from Pieter Xavery's 1673 set depicting the Leiden vierschaar.