In his Political Treatise, Benedict de Spinoza (1632-1677) describes a
frame of government for a federal polity whose members are neither ''
confederated'' nor ''united'' but are ''mutually associated and united
.'' Spinoza regards the federal polity as the preferred mode of republ
ican government. His Political Treatise marks the turn in political sc
ience from the classic polls to the extended republic of modern times.
His argument converges with and illuminates that of The Federalist in
several respects. This article discusses Spinoza's contributions to t
he federal idea, and shows the importance of federalism for understand
ing Spinoza.