In the Middle Ages, the Church and the worldly authorities were closely related. Martin Luther separated the religious and the worldly realms in principle (doctrine of the two kingdoms). The believers were obliged to use reason to govern the worldly sphere in an orderly and peaceful way. Luther's doctrine of the priesthood of all believers upgraded the role of laymen in the church considerably. The members of a congregation had the right to elect a minister and, if necessary, to vote for his dismissal (Treatise On the right and authority of a Christian assembly or congregation to judge all doctrines and to call, install and dismiss teachers, as testified in Scripture; 1523). Calvin strengthened this basically democratic approach by including elected laymen (church elders, presbyters) in his representative church government. The Huguenots added regional synods and a national synod, whose members were elected by the congregations, to Calvin's system of church self-government. This system was taken over by the other reformed churches.
Who added the election of laymen to church government?
Calvin

The Roman Republic (Latin: Res publica Romana; Classical Latin: [res pub.l.ka roma.na]) was the period of ancient Roman civilization beginning with the overthrow of the Roman Kingdom, traditionally dated to 509 BC, and ending in 27 BC with the establishment of the Roman Empire. It was during this period that Rome's control expanded from the city's immediate surroundings to hegemony over the entire Mediterranean world. During the first two centuries of its existence, the Roman Republic expanded through a combination of conquest and alliance, from central Italy to the entire Italian peninsula. By the following century, it included North Africa, Spain, and what is now southern France. Two centuries after that, towards the end of the 1st century BC, it included the rest of modern France, Greece, and much of the eastern Mediterranean. By this time, internal tensions led to a series of civil wars, culminating with the assassination of Julius Caesar, which led to the transition from republic to empire. The exact date of transition can be a matter of interpretation. Historians have variously proposed Julius Caesar's crossing of the Rubicon River in 49 BC, Caesar's appointment as dictator for life in 44 BC, and the defeat of Mark Antony and Cleopatra at the Battle of Actium in 31 BC. However, most use the same date as did the ancient Romans themselves, the Roman Senate's grant of extraordinary powers to Octavian and his adopting the title Augustus in 27 BC, as the defining event ending the Republic.
When was Cleopatra defeated at the Battle of Actium?
31 BC

The Republic of Letters was the sum of a number of Enlightenment ideals: an egalitarian realm governed by knowledge that could act across political boundaries and rival state power. It was a forum that supported "free public examination of questions regarding religion or legislation". Immanuel Kant considered written communication essential to his conception of the public sphere; once everyone was a part of the "reading public", then society could be said to be enlightened. The people who participated in the Republic of Letters, such as Diderot and Voltaire, are frequently known today as important Enlightenment figures. Indeed, the men who wrote Diderot's Encyclopedie arguably formed a microcosm of the larger "republic".
Who were two of the figures that participated in the Republic of Letters?
Diderot and Voltaire