Question

billy is trying to convince cynthia that all whole numbers are also natural numbers. to support his argument, billy points out that 1,2,3,4,5 and 6 are all whole numbers and are also natural numbers. he goes on to argue that, by continuing the pattern, every integer greater than 6 will also be both a whole number and a natural number, thus making all whole numbers natural numbers. where did billy made his error?