This book offers a new and radical interpretation of the core of Spinoza's metaphysics. The first half of the book, which concentrates on the metaphysics of substance, suggests a new reading of Spinoza's key concepts of Substance and Mode, of Spinoza's pantheism and monism, and of his understanding of causation. The second half, addresses Spinoza's metaphysics of Thought, and presents three bold and interrelated theses on Spinoza's two doctrines of parallelism, the multifaceted structure of ideas, and Spinoza's reasons for holding that we cannot know any attributes of God, or Nature, other than Thought and Extension. Finally, the author shows that Spinoza assigns clear priority to the attribute of Thought without embracing reductive idealism.