Chapters: 1. Introduction: Intensional Mathematics and Constructive Mathematics (S. Shapiro). 2. Epistemic and Intuitionistic Arithmetic (S. Shapiro). 3. Intensional Set Theory (J. Myhill). 4. A Genuinely Intensional Set Theory (N.D. Goodman). 5. Extending Gödel's Modal Interpretation to Type Theory and Set Theory (A. Ščedrov). 6. Church's Thesis is Consistent with Epistemic Arithmetic (R.C. Flagg). 7. Calculable Natural Numbers (V. Lifschitz). 8. Modality and Self-Reference (R.M. Smullyan). 9. Some Principles Related to Löb's Theorem (R.M. Smullyan).