[raherakty]

Well, as you said, math is an invention of man. We've created the rules and the sets of numbers that go along with it. There's no reason why you couldn't create a number system without a zero, if that's what you wanted to do. However, a number system that does not have a zero isn't going to be of much use in today's world. How will you express the numerical value of an empty bank account? The velocity, in meters per second, of a stationary object? The number of apples remaining at your store if you start with five and sell five? From a verbal perspective, you could write a verbal response: no money, no velocity, no apples. From a mathematical perspective, the number system is now broken, because you cannot represent the answer of five minus five in numbers anymore. As I said above, you can find weird ways around having a zero, but then doing relatively simple things like solving quadratic equations becomes hopelessly complex as you bend over backwards to try to avoid having a number with no numerical value.

We've all come to accept the simplification of mathematics that comes along with having a zero, while brushing aside questions like "how can you have zero of something?" Now, whether it makes sense to say something along the lines of "I have zero apples," that's a question for the philosophers, as Rythm pointed out above.