This curious property is one reason some scholars rejected the concept of infinite sets more than 100 years ago. For example, the set of even numbers E = {0, 2, 4, 6, …} is a proper subset of ...

For example, the number line is infinite, regardless of whether you start it at –∞, 0 or 1. ... In this way, Cantor also studied the cardinality of infinite sets. For example, ...