He is best known for his 1603 work, "Politica Methodice Digesta, Atque Exemplis Sacris et Profanis Illustrata"; revised editions were published in 1610 and 1614. The ideas expressed therein have led many to consider him one of the first true federalists, as the greatest intellectual thinker in the early development of federalism in the 16th and 17th centuries and the construction of subsidiarity.
Althusius was born about 1563, to a family of modest means in Diedenshausen, County Sayn-Wittgenstein (Siegen-Wittgenstein), a Calvinist County in what is now the state of North Rhine Westphalia but was then the seat of an independent Grafschaft or County. Under the patronage of a local count, he attended the Gymnasium Philippinum in Marburg from 1577 and began his studies in 1581, concentrating in law, philosophy, and logic, first in Cologne, then in Basel and probably with study excursion in Geneva 1585/1586.
In 1586, after completing his studies, Althusius joined the law faculty at the Protestant-Calvinist Herborn Academy of Nassau County, from 1592 to 1596 he changed to the Calvinist Academy in Burgsteinfurt/Westphalia, and after return he was appointed president of the Nassau College in Siegen (removed in this town from 1594 to 1600) in 1599/1600 and in Herborn in 1602,  also beginning his political career by serving as a member of the Nassau (Germany) county council. For the next several years, he became involved in various colleges throughout the area, variously serving as their president and lecturing on law and philosophy, and in 1603, he was elected to be a municipal trustee of the city of Emden, in East Frisia, where he ultimately made his fame. He became a city Syndic in 1604, which placed him at the helm of Emden's governance until his death.
Johannes Althusius died on August 12, 1638, in Emden.
By the time Althusius began his formal studies in 1581, the Dutch Revolt against Spain had already come to a head, and it was not to be settled until Dutch independence was recognized in 1609. Because the nature of the conflict was largely religious – Calvinist states rebelling against their Catholic overlords – it was of especial interest to Calvinist political thinkers such as Althusius.
In the late sixteenth and early seventeenth centuries, Emden in East Frisia (now Germany) was at the crossroads of political and religious activity in the region. A prosperous seaport situated between the Netherlands and the Holy Roman Empire, with convenient maritime access to England, Emden was a prominent city in the politics and policy of all three nations, and was thus able to retain a significant amount of political freedom. It was located within the overlapping territories of the Catholic Habsburg emperor and a Lutheran provincial lord, but its population was mainly Calvinist, and the city had a strong Calvinist spirit. Emden also played host to two Protestant synods, first in 1571 and again in 1610, and was widely regarded as the ‘Geneva of the North’ or the ‘alma mater’ of the Dutch Reformed Church. These attributes made the city the ideal place for Althusius to propose his particular brand of political philosophy; Emden's theological and political prominence coupled with its yen for religious and civic independence made the Althusian political theory both topical and popular.
The Politica, the first edition of which was completed in 1603, is considered not only the most fully developed scheme of Calvinist political theory, but also the only systematic justification of the Dutch Revolt. Althusius took from thinkers in various fields, including Aristotle, Calvin, Bodin, Machiavelli, Grotius, and Peter Ramus; Politica cited close to 200 books in all.
The first edition of Politica was received with wide acclaim in Emden and in the Netherlands beyond.
The publishing of the most recent edition of Politica was funded by the American libertarian think tank Liberty Fund. The controversy comes from the placement of the word 'association'. Most scholars would argue that this is a misrepresentation of his meaning and the word consociation is more appropriate because Althusius was referring to social groups that you cannot remove yourself from rather than associations by choice. The term 'consociatio' was used by the political scientist Arend Lijphart to give name to stable democratic systems in deeply divided societies: consociationalism.
He was married in 1596 in Siegen to Margarethe Neurath (born 1574), with whom he had at least six children.
- Johannes Althusius, Politica, Frederick Smith Carney (Editor), Liberty Fund, 1997
- Johannes Althusius, La politica, ed. Corrado Malandrino, Francesco Ingravalle, Mauro Povero, complete Latin text and Italian translation, Turin, Claudiana, 2009.
- "Il lessico della Politica di Johannes Althusius", a cura di Francesco Ingravalle e Corrado Malandrino, Firenze, Olschki, 2005.
- Follesdal, Andres. "Survey Article: Subsidiarity." Journal of Political Philosophy 6 (June 1998): 190-219.
- Friedrich, Carl J. Constitutional Reason of State. Providence: Brown University Press, 1957.
- Hueglin, Thomas. "Covenant and Federalism in the Politics of Althusius." In The Covenant Connection: From Federal Theology to Modern Federalism, ed. Daniel J. Elazar and John Kincaid, 31-54. Lanham, Maryland: Lexington Books, 2000.
- Hueglin, Thomas. Early Modern Concepts for a Late Modern World: Althusius on Community and Federalism. Waterloo, Ont.: Wilfrid Laurier University Press, 1999.
- ________. "Federalism at the Crossroads: Old Meanings, New Significance." Canadian Journal of Political Science 36 (June 2003): 275-293.
- ________. "Have We Studied the Wrong Authors? On Johannes Althusius as a Political Theorist." Studies in Political Thought 1 (Winter 1992): 75-93.
- Lakoff, Sanford. "Althusius, Johannes." In Political Philosophy: Theories, Thinkers, and Concepts. Edited by Seymour Martin Lipset, 221-223. Washington, D.C.: CQ Press, 2001.
- von Gierke, Otto. The Development of Political Theory. Translated by Bernard Freyd. New York: W. W. Norton and Company, Inc., 1939.