This is a study of the reasons behind Spinoza's excommunication from the Portuguese–Jewish community of Amsterdam in 1656. The central question in the book is how and why did the issue of the immortality of the soul play a role in the decision to excommunicate Spinoza. The work begins with a discussion of the nature of cherem or banning within Judaism, and in the Amsterdam community, in particular, as well as of a number of possible explanations for Spinoza's ban. It then turns to the variety of traditions in Jewish religious and philosophical thought on the post‐mortem fate of the soul and the after life. This is followed by an examination of Spinoza's own views on the eternity of the mind in the Ethics and the role that the denial of personal immortality plays in his overall philosophical and political project. Part of the book's argument is that Spinoza's views were not only an outgrowth of his own metaphysical principles, but also a culmination of an intellectualist trend in medieval Jewish rationalism (especially Maimonides and Gersonides).