If we rely on the students' assumption of pattern here, it would be sensible to conclude that 00=1. However,00 is undefined (Edwards and Penny 1994; Keedy, Bittinger,and Smith 1982). So pattern logic worked before, but it does not now. This result raises more mathematical and pedagogical questions: Could a teacher explain why pattern logic works sometimes but not all the time? Why is it appropriate to use patterns to explain the multiplication of negative number but not 00? Are we using this pattern in an attempt to make students comfortable with the idea that the product of two negative numbers is a positive number, or are we using to set them up for success in mathematical reasoning?