Kant’s theory of cognition aimed to explain the possibility of scientific knowledge. Aesthetics and life science were not considered by Kant in the context of cognition. By contrast, Cassirer set himself a philosophical task to extend Kant’s theory of cognition to all forms of culture, including pre-scientific knowledge and aesthetics. The present study demonstrates how Cassirer explained the possibility of different objective forms, named symbolic, by employing and transforming Kant’s theory of cognition. For this goal, Cassirer took the following steps: modified the definitions of a priori synthesis (the act of understanding) and pure intuition (the forms of space and time) - main building blocks of Kant’s cognition; indicated the necessary correlation of intuition and synthesis; characterized a priori synthesis and the intuition as notions which include contradicted meanings. Cassirer called this contradiction “twofold oppositions” as characteristic of a priori synthesis. The first argument of the article is that the possibility of various synthetic acts is rooted in the nature of a priori synthesis which carries together two different meanings: the act of uniting elements and the initial unity. One synthetic act forms the world of nature and is connected to scientific space and time, and the other is the product of immediate perceptional space and time, from which the world of myth and aesthetics appears. Thus, Cassirer expanded the scope of “pure” synthesis. The second argument is that Cassirer specified a priori synthesis and pure intuition as a functional concept. The functional concept belongs to the model of concept as-relation that Cassirer has elaborated. It includes moments that are separated and united simultaneously. This definition of concept breaks the rules of consistency. The concept of as-relation justifies the contradictory characteristics of a priori synthesis and pure intuition, which include both the combination of moments in a synthesizing act and the initial unity of intuition.