Definition:Set Theory/Historical Note

Historical Note on Set Theory
Set theory arose from an attempt to comprehend the question: "What is a number?"

The main initial development of the subject was in fact not directly generated as a result of trying to answer this question, but as a result of 's work around $1870$ to understand the nature of infinite series and related subjects.

As a result of this he began to consider the nature of infinite collections of general object, not just numbers.

In $1873$, discovered that the set of algebraic reals is countable.

Soon after that, he discovered that the set of all real numbers is uncountable.

The concepts of equipotent sets, order isomorphic structures, cardinals and ordinals are all due to.


 *  ....is usually considered the founder of set theory as a mathematical discipline ...
 * -- : (1960, 2nd ed. 1972)