Metaphysics is the study of the most basic questions about reality, about what there is: our program for this unit. Numbers appear to be real public objects, nonspatial, eternal, and not perceptible but knowable by the mind or intellect. Use numbers to count physical objects, but are not physical objects themselves. If they were just the contents of our minds then we would each have our own 2,3,4,5 If it were true that numbers were just mental, then they would not have existed before there were minds. Numbers must be public objects, non physical, eternal, independent of our minds, but not located in physical space. Number seem to be public but nonspatial objects. Not objects of perception, but objects of thought. Unlike physical things they don"t perish, they exist forever. Unlike physical things they aren"t perceived, they are known. Unlike with physical things we can be completely certain about their existence and their nature.