This chapter contains sections titled: * The Fitness of the Environment * The Chemical Composition of the Cosmos * The Birth of the Elements * Epilogue: Planetary Habitats * Notes.

This chapter contains sections titled: * Aristotle’s Errors * The Myth of the Flat Earth * The Copernican Transformation * The Tychonian Transition * The “Universe Based on Causes” of Johannes Kepler * Galileo and the Telescope * Newton, the Ultimate Unifier * Note.

Ptolemy's Almagest, a brilliant treatise on theoretical astronomy combined with a practical handbook for computation, includes many compromises to reconcile discordant observations. This defense of Ptolemy examines in some detail a critical case concerning the model for Venus, which has sometimes been used as evidence for Ptolemy's perfidy. There the Alexandrian astronomer demonstrated his ingenuity when orbital constraints made it impossible to obtain directly the observed configurations he might have preferred.