In Mathematical Thought and Its Objects, Charles Parsons examines the notion of object, with the aim to navigate between nominalism, denying that distinctively mathematical objects exist, and forms of Platonism that postulate a transcendent realm of such objects. He introduces the central mathematical notion of structure and defends a version of the structuralist view of mathematical objects, according to which their existence is relative to a structure and they have no more of a “nature” than that confers on them.
Just a quote from his father about social objects: A normative concept is not abstract only in the sense that, for instance, the conception of a frictionless machine is abstract, that, for purposes of the analysis in hand, it does not at the moment exist. It is further abstract in the sense that if it did, or could, exist apart from action in the particular concrete context in question, it could not have normative significance, for a normative concept always refers factually to a state of affairs which in some respects requires action to bring about or maintain. At least in the terms employed by the theory of mechanics, the idea of a frictionless machine can have no influence on the behavior of wheels, rods, cylinders and valves; this idea does not operate to reduce the amount of friction except through the mind of an engineer, that is by a process of action. But there is every reason to believe that the idea of "equality" influences the behavior of human beings and actually in certain respects operates to reduce the degree of inequality.