The point was - you can't check everything beforehand. No matter how hard you try, there's always a non-zero probability that a bug will "prove Einstein wrong",

The point was - you can't check everything beforehand. No matter how hard you try, there's always a non-zero probability that a bug will "prove Einstein wrong", or drive people into a ditch, or find horribly mismatched partners on a dating site, or explode toasters and kill puppies.