Two classic essays by great German mathematician: one provides an arithmetic, rigorous foundation for the irrational numbers, the other is an attempt to give the logical basis for transfinite numbers and properties of the natural numbers.

I. Continuity and Irrational Numbers Preface
1. Properties of Rational Numbers
2. Comparison of the Rational Numbers with the Points of a Straight Line
3. Continuity of the Straight Line
4. Creation of Irrational Numbers
5. Continuity of the Domain of Real Numbers
6. Operations with Real Numbers
7. Infinitesimal Analysis
II. The Nature and Meaning of Numbers
Prefaces
1. Systems of Elements
2. Transformation of a System
3. Similarity of a Transformation. Similar Systems
4. Transformation of a System in Itself
5. The Finite and Infinite
6. Simply Infinite Systems. Series of Natural Numbers
7. Greater and Less Numbers
8. Finite and Infinite Parts of the Number-Series
9. Definition of a Transformation of the Number-Series by Induction
10. The Class of Simply Infinite Systems
11. Addition of Numbers
12. Multiplication of Numbers
13. Involution of Numbers
14. Number of the Elements of a Finite System