The truth of the fact is that math is merely a social construct. Reality is interdependent on subjective interpretation. That is to say that our perceptions define reality insofar as reality itself is defined subjectively. It's a circular argument, but it applies logically. For example, what does the word "truth" mean? What does the word "logic" mean? They are "defined" perceptually (subjectively) just as reality is "defined" perceptually. The properties of a car, for example, in terms of an "objective purpose", are entirely subjective. For example, the idea of the car (as an object that allows you to get from A to B) is a subjective interpretation. That's why "reality" exists in the mind.