Cantor's Diagonal Argument is a mathematical proof that demonstrates the existence of different sizes of infinity, specifically showing that the set of real numbers is uncountably infinite, unlike the set of natural numbers, which is countably infinite. The argument begins by assuming that all real numbers can be listed in a sequence. Cantor then constructs a new real number by altering the -th digit of the -th number in the list, ensuring that this new number differs from every number in the list at least at one decimal place. This construction leads to a contradiction because the newly created number cannot be found in the original list, implying that the assumption was incorrect. Consequently, there are more real numbers than natural numbers, highlighting that not all infinities are equal. Thus, Cantor's argument illustrates the concept of uncountable infinity, a foundational idea in set theory.
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