| Preface | p. xiii |
| Introduction | p. xxv |
| Euclid's Geometry | p. 1 |
| Very Brief Survey of the Beginnings of Geometry | p. 1 |
| The Pythagoreans | p. 3 |
| Plato | p. 5 |
| Euclid of Alexandria | p. 7 |
| The Axiomatic Method | p. 9 |
| Undefined Terms | p. 11 |
| Euclid's First Four Postulates | p. 15 |
| The Parallel Postulate | p. 20 |
| Attempts to Prove the Parallel Postulate | p. 23 |
| The Danger in Diagrams | p. 25 |
| The Power of Diagrams | p. 27 |
| Straightedge-and-Compass Constructions, Briefly | p. 29 |
| Descartes' Analytic Geometry and Broader Idea of Constructions | p. 34 |
| Briefly on the Number [pi] | p. 38 |
| Conclusion | p. 40 |
| Logic and Incidence Geometry | p. 53 |
| Elementary Logic | p. 53 |
| Theorems and Proofs | p. 55 |
| RAA Proofs | p. 58 |
| Negation | p. 60 |
| Quantifiers | p. 61 |
| Implication | p. 64 |
| Law of Excluded Middle and Proof by Cases | p. 65 |
| Brief Historical Remarks | p. 66 |
| Incidence Geometry | p. 69 |
| Models | p. 72 |
| Consistency | p. 76 |
| Isomorphism of Models | p. 79 |
| Projective and Affine Planes | p. 81 |
| Brief History of Real Projective Geometry | p. 89 |
| Conclusion | p. 90 |
| Hilbert's Axioms | p. 103 |
| Flaws in Euclid | p. 103 |
| Axioms of Betweenness | p. 105 |
| Axioms of Congruence | p. 119 |
| Axioms of Continuity | p. 129 |
| Hilbert's Euclidean Axiom of Parallelism | p. 138 |
| Conclusion | p. 142 |
| Neutral Geometry | p. 161 |
| Geometry Without a Parallel Axiom | p. 161 |
| Alternate Interior Angle Theorem | p. 162 |
| Exterior Angle Theorem | p. 164 |
| Measure of Angles and Segments | p. 169 |
| Equivalence of Euclidean Parallel Postulates | p. 173 |
| Saccheri and Lambert Quadrilaterals | p. 176 |
| Angle Sum of a Triangle | p. 183 |
| Conclusion | p. 190 |
| History of the Parallel Postulate | p. 209 |
| Review | p. 209 |
| Proclus | p. 210 |
| Equidistance | p. 213 |
| Wallis | p. 214 |
| Saccheri | p. 218 |
| Clairaut's Axiom and Proclus' Theorem | p. 219 |
| Legendre | p. 221 |
| Lambert and Taurinus | p. 223 |
| Farkas Bolyai | p. 225 |
| The Discovery of Non-Euclidean Geometry | p. 239 |
| Janos Bolyai | p. 239 |
| Gauss | p. 242 |
| Lobachevsky | p. 245 |
| Subsequent Developments | p. 248 |
| Non-Euclidean Hilbert Planes | p. 249 |
| The Defect | p. 252 |
| Similar Triangles | p. 253 |
| Parallels Which Admit a Common Perpendicular | p. 254 |
| Limiting Parallel Rays, Hyperbolic Planes | p. 257 |
| Classification of Parallels | p. 262 |
| Strange New Universe? | p. 264 |
| Independence of the Parallel Postulate | p. 289 |
| Consistency of Hyperbolic Geometry | p. 289 |
| Beltrami's Interpretation | p. 293 |
| The Beltrami-Klein Model | p. 297 |
| The Poincare Models | p. 302 |
| Perpendicularity in the Beltrami-Klein Model | p. 308 |
| A Model of the Hyperbolic Plane from Physics | p. 311 |
| Inversion in Circles, Poincare Congruence | p. 313 |
| The Projective Nature of the Beltrami-Klein Model | p. 333 |
| Conclusion | p. 346 |
| Philosophical Implications, Fruitful Applications | p. 371 |
| What Is the Geometry of Physical Space? | p. 371 |
| What Is Mathematics About? | p. 374 |
| The Controversy about the Foundations of Mathematics | p. 376 |
| The Meaning | p. 380 |
| The Fruitfulness of Hyperbolic Geometry for Other Branches of Mathematics, Cosmology, and Art | p. 382 |
| Geometric Transformations | p. 397 |
| Klein's Erlanger Programme | p. 397 |
| Groups | p. 399 |
| Applications to Geometric Problems | p. 403 |
| Motions and Similarities | p. 408 |
| Reflections | p. 411 |
| Rotations | p. 414 |
| Translations | p. 417 |
| Half-Turns | p. 420 |
| Ideal Points in the Hyperbolic Plane | p. 422 |
| Parallel Displacements | p. 424 |
| Glides | p. 426 |
| Classification of Motions | p. 427 |
| Automorphisms of the Cartesian Model | p. 431 |
| Motions in the Poincare Model | p. 436 |
| Congruence Described by Motions | p. 444 |
| Symmetry | p. 448 |
| Further Results in Real Hyperbolic Geometry | p. 475 |
| Area and Defect | p. 476 |
| The Angle of Parallelism | p. 480 |
| Cycles | p. 481 |
| The Curvature of the Hyperbolic Plane | p. 483 |
| Hyperbolic Trigonometry | p. 487 |
| Circumference and Area of a Circle | p. 496 |
| Saccheri and Lambert Quadrilaterals | p. 500 |
| Coordinates in the Real Hyperbolic Plane | p. 507 |
| The Circumscribed Cycle of a Triangle | p. 515 |
| Bolyai's Constructions in the Hyperbolic Plane | p. 520 |
| Elliptic and Other Riemannian Geometries | p. 541 |
| Hilbert's Geometry Without Real Numbers | p. 571 |
| Axioms | p. 597 |
| Bibliography | p. 603 |
| Symbols | p. 611 |
| Name Index | p. 613 |
| Subject Index | p. 617 |
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