  Earlier Schlick had argued that knowledge consists in the identification of that which is known with that as which it is known or, in other words, knowledge consists in the relation of one thing to some other thing, as which it is known. And this is only achieved when one of the objects which is known is, in turn, related to still others, as it is in the myriad spatio-temporal relations in which it stands to other objects. Ultimately, all these relations can be known quantitatively by specifying a number of magnitudes, thus reducing the relations of the objective spatio-temporal order to quantities. Of course, this cannot be achieved within the qualitative order since the different relations of position and temporal order are qualitatively different and cannot, for that very reason, be compared. But the entities populating the objective spatio-temporal order are wholly unlike the denizens of the subjective realm which are the intuitive objects of experience, the immediately given sensory data. Both may be univocally designated by implicitly defined concepts and both kinds of entities are, therefore, objects of possible knowledge. As such, intuitive contents are attributed full reality and, in addition, the objects populating the spatio-temporal order, the entities of advanced theoretical science, are just as real as the contents of consciousness with which they are correlated.