Some fifty years after the outbreak of a rebellion against the central government of King Philip II of Spain and about thirty years after the Republic of the Seven United Provinces was established as a result of that rebellion, the new independent state went through its first grave internal crisis. The crisis centered on fundamental matters concerning the nature and essence of the country.

For a long time, the struggle with Spain had ensured that the Dutch provinces acted as single body. Their differences remained in the background because they were outweighed by their common interests. The situation changed when the direct military threat waned and especially when the Republic and the King of Spain concluded the Twelve Years' Truce in 1609. Internal differences of opinion then began to emerge. They concerned matters of a fundamental nature: the character of the official Reformed Church, also with respect to other religious persuasions, the relationship between Church and State and, eventually, the essence of the State itself.

The Calvinist variant of Protestantism had been a driving force behind the rebellion against Spain. Especially in the southern part of the Low Countries, Calvinism had developed into a strong, militant movement. This, however was precisely the territory Spain regained control of after 1580. As a result, many radical Calvinists fled to the free northern provinces. There, and particularly in the key province of Holland, the rulers adopted a pragmatic attitude: nobody was forced to convert to the new religion. Under these circumstances, the fight against Spain could rely on widespread support and trade could flourish. The strict Calvinists, on the other hand, aimed at establishing a uniform Calvinistic society, allowing no latitude for other religious beliefs. For this reason, they wanted to gain control of the state.

The religious differences came to light when a conflict arose about predestination, which is an important pillar of Calvinistic doctrine: God determines in advance who is to go to heaven and who is not; what a person does during his life on Earth has no influence on his destiny. In 1604, Jacobus Arminius, a professor of theology at the University of Leiden, argued that every individual's life, actions, and beliefs - his free will - could also determine whether he would go to heaven or not. His colleague, Franciscus Gomarus, became his fiercest opponent. The Arminianen, as Arminius' followers were called, made their viewpoint known in 1610 at a so-called Remonstrance. Since then, they are most often referred to as Remonstrants and, later on, also as Rekkelijken (moderates). The Gomaristen (Gomarius' followers) have been called Counter-Remonstrants (i.e. orthodox) ever since.

A second essential question arose in this connection: did the Republic constitute a confederation of states (the provinces) that were in fact independent, or was it first and foremost a union in which the provinces enjoyed only limited freedom? This matter was of utmost importance, among other things because the freedom and the privileges of the individual provinces had been one of the main reasons for the rebellion against King Philip II. The province of Holland chose the principle of individual freedom. The chief minister Johan van Oldenbarnevelt, Holland's mightiest politician, propagated this view with all the power he had. The other six provinces, however, disagreed, as did Prince Maurice of Orange. The authority of the Stadholder, commander in chief of the Republic's army and navy, was based on the unity of the provinces, after all. In 1616 the Prince began to turn against his chief minister Van Oldenbarnevelt,. The man whose politics had been so determinative in ensuring the young Republic's success at the very beginning of the 17th century, now faced defeat, together with Holland. The conflict reached its peak and, in many respects, also its end, when the elderly statesman - aged 71 at the time - was beheaded on 13 May 1619 on charges of high treason.

The Republic also straightened things out with respect to religious matters. In November 1618, the States General of Dordrecht, led by Prince Maurice, convened a synod. In April 1619, its members took a number of momentous decisions with regard to the position of the church in the Netherlands: all of Arminius' ideas were condemned.
This way, the unity of both the young Republic and the Dutch Reformed Church were firmly established in 1619. The authorities' support played a crucial role in these decisions. Afterwards, the authorities ensured they did not loose their grip on the Church; the spirit of pragmatism and moderation continued to prevail. Not only was the Church required to adapt to these views, but Prince Maurice had to as well. In spite of his having vanquished Van Oldenbarnevelt and his supporters - among whom the famous lawyer and scholar Hugo de Groot, better known as Hugo Grotius, the Republic remained a confederation of provinces working together, without an authoritarian ruler, as was the case everywhere else. The citizens went on deciding the course of events in the Netherlands, even in the years after 1619.