Mathematical axioms and postulates can be used to define addition, particularly through the concept of succession in natural numbers. By defining an operation that identifies the "next" number in a set, one can establish a framework for addition without initially labeling it as such. This leads to the conclusion that 1+1 equals 2 through repeated succession. While set theory isn't necessary for this basic proof, it can help validate the rules of integer addition. Ultimately, one can also define the number 2 as the result of 1+1.