The notion of infinity has fascinated philosophers, scientists, and mathematicians for millennia. Its enigmatic nature seemed to thwart all attempts to unlock its secrets. Scriptural allusions to the infinite evoke a similar sense of mystery. Few have been as intrigued by the concept of infinity—or as tenacious in trying to understand it—as the German mathematician Georg Cantor. Between 1874 and 1884, Cantor published numerous papers that illuminated some of the shadowy regions of the infinite. He discovered a remarkable realm where half of a pie is as large as the whole, infinity comes in different sizes, and miracles are mathematically plausible.