But is this the right way to solve the problem? No its not! Nowhere in the problem, except in the question, is the word fish found. Thus the fifth pet might just as well be elephants as fish. After a lot of work you can safely conclude that the German has the fifth pet, but you have to ASSUME that the fifth pet is fish in order to conclude the German has fish. But you have no basis for making this assumption. Note that Einstein was very careful to separate the “Facts” from the “Question” in this puzzle.

So the correct answer to the Einstein Quiz is: You have no idea if anyone keeps fish or not. Once you grasp the nature of the problem correctly, its rather simple to solve. And it is just like Einstein to give us a puzzle like this, for he stressed examining assumptions, and once wrote: “The important thing is to not stop questioning.”