Objectivity, the property of being an object of human knowledge, has many senses. In the first place, it can mean the property of being valid for a general public; its contrary being the subjectivity of the private, individual and incommunicable act. This kind of objectivity, which we call public objectivity, is necessary for objects of natural science. There are, however, two kinds of public objectivity. One belongs to an idea (or concept), and the other belongs to a reality in its World. The former is that property possessed by an exact and precise definition, namely, of being independent of particular places, times and factual occurrences; this belongs not to any World of the real, but to the realm of ideas. The latter, however, belongs to a shared World of real things. It is the object of factual judgements, founded upon perception and — unlike the precision of an idea — it is accompanied by an irreducible element of impreciseness and indeterminateness.