Just as absolutely singular things do actually exist; however they do so thanks to the existence of universal principles of existence. Do these principles “exist”? Of course, but in a very especial sense. Thus there is no knowledge without regard to the most universal , given by intelectual intuition,  and the most singular being (anything) at the same time, given by empirical perception , both togheter. 

This ontological-epistemological fact underlies our whole historical and personal attempts in this whole human existence.