>>4
Let's assume there such a largest number n.
Peano's axioms state that n has a successor (which we can call n' or n+1 in simpler terms) which is how we define a greater number. Contradiction.
There is no greatest number in N, but there is the smallest number 0.
If you try to define the set as finite, you'll end up with the same trivial contradiction which shows that there will always be more elements.
I'm guessing you reject any kind of inductive reasoning as well, and you don't accept any abstract concepts unless they are present in this one specific mathematical object we call our universe.