Theorem: There are no boring numbers.
Proof by Contradiction. Assume that there were a non-empty set B which is a subset of all boring natural numbers. Like all subsets of natural numbers, this set as a minimum number b. Being the smallest boring natural number b is in fact interesting and therefore not boring after all. A contradiction!
Therefore, the theorem above is true.
Note: Although the theorem above is for obviously for fun, you must know proof by contradiction in order to fully appreciate it.