At his death, Spinoza left two major works, very different from one another. The first is the Ethics, rigorously set out in geometrical terms, with definitions, axioms, and theorems. In the Ethics, Spinoza takes the reader down the path of reason to an ultimate beatitude, a rational salvation, a kind of peace of mind attained through the true knowledge of God, oneself, and one's place in the world. The other is of a very different sort. The Tractatus...