Primes, quite literally, drove people insane, particularly as so many puzzles remained. They knew a prime was a whole number that could only be divided by one or itself, but after that they hit all kinds of problems. For instance, they knew that the total of all primes was precisely the same as the total of all numbers, as both were infinite. This was, for a human, a very puzzling fact, as surely there must be more numbers than prime numbers.
