Spinoza’s metaphysics is primarily to be found in his mature masterpiece, Ethica, Ordine Geometrico Demonstrate, or Ethics Demonstrated in Geometric Order. Begun in the early 1660s, worked on into the 1670s, and published in the Opera Posthuma of 1677, it is a systematic treatment of the substantial nature of God and of the relationship to it of the human mind, emotions, and freedom. These topics echo the title of an earlier Dutch work, the Short Treatise on God, Man, and His Well-Being. Two other relevant works are the methodological Tractatus de Intellectus Emendatione (1677), or Treatise on the Emendation of the Intellect, and the Tractatus Theologico-Politicus, or Theologico-Political Treatise (published anonymously, 1670). Finally, Spinoza’s correspondence and, though not completely reliable as a source of his own views, the exposition of Descartes’ Principles of Philosophy (1663), with its appended Metaphysical Thoughts, are of help in understanding the Ethics.