Spinoza's Political Treatise constitutes the very last stage in the development of his thought, as he left the manuscript incomplete at the time of his death in 1677. On several crucial issues - for example, the new conception of the 'free multitude' - the work goes well beyond his Theological Political Treatise (1670), and arguably presents ideas that were not fully developed even in his Ethics. This volume of newly commissioned essays on the Political Treatise is the first collection in English to be dedicated specifically to the work, ranging over topics including political explanation, national religion, the civil state, vengeance, aristocratic government, and political luck. It will be a major resource for scholars who are interested in this important but still neglected work, and in Spinoza's political philosophy more generally.